Hardly a day goes by where we do not see in the news yet another tragic loss of children, in automobile accidents, often due to drunk driving, incredible murders (all four children in one family in Oklahoma, along with their mother), tragic illnesses or mishaps (such as drowning in pools), and other ailments that result in the loss of a young life.
I've written before about his to console those who are bearing the unbearable. Nothing can really ease the loss of a child. However, I realize that it helps if I can assure those who mourn of several things.
One is that no matter how horribly the child may have been frightened or in pain, they enter heaven unafraid and with no thought of the pain or trauma of their passing. It's not that they "forget" or have memories erased or anything. Rather, heaven is so awesome that it truly washes away the attention completely from the sadness and pain and they are only focused on looking forward, at the "here and now" of heaven. You know how when you do something you truly enjoy that you are totally absorbed and content, and even for just a few moments don't think of your problems? It is like that but a million times better! The child does not need to have memories erased or to be soothed because the child's soul is refreshed instantly at being in the place that is only love and light.
Second, this is true even if your child was raised, as far too many are, without any knowledge of the genuine faith and nature of the one God. It's not like when they arrive they are confused and scared because all that they had been taught was wrong, or that they have a total blank slate about the faith due to lack of traditional faith transmission by parents and caregivers. First of all, they have an instinctive recognition of God, and they feel from the start that they always knew about him. Why is that? Well, remember that their guardian angels were always with them when alive, so having a guardian angel is like hearing God talking or humming in the background, even if one is not a believer. It's that feeling you have that you are never really alone (the comforting feeling, not the feeling that paranoids or stalking victims have, ha). No, all people have that white noise access to God even if they do not believe, due to their guardian angel and also the constant efforts of the Holy Spirit to reach everyone.
Because young children are innocent they cannot be held to blame for not receiving instruction in God and the true faith. Thus their instinctive connectivity via their guardian angel is pure, and they feel at home and "knowledgeable" right away in heaven. Jesus himself assured the disciples that the angels of children constantly face God. Adults are another matter entirely, who have their own accountability for ignoring the faith. Children, however, cannot help how they are raised, but a parent or caregiver who is suffering the loss of a child does not need to worry that their being remiss in teaching them the faith has caused them to now be scared or in pain after suddenly dying. Their guardian angel is with them right to heaven, as the angel was with them in the womb before they even "knew" they were a person. (Just think, mothers of twins, triplets and other multiple births have that many guardian angels along for the ride too :-) However, this is no excuse not to raise any living child in the faith because children need knowledge of God and faith in him in order to live properly and fully. Faith is about living and all children need the support and love of knowledge of God to live full and rational lives. So I am making these points in order to reassure those who were remiss in teaching their children, and who are in pain of loss, and not to tell parents of living children that it is "OK" to skip the faith and God part and it all sorts itself out anyway. That is because you hope your child will grow up to be adults, and then it is an entirely different matter.
However, if the worst happens, be assured that children do not need to know about God in order to find him and not be afraid when they die. After all, premature, aborted and newborn babies who die all find their way to heaven without having any knowledge about life at all, say nothing of instruction in the faith. In heaven babies are aware in a way that I can't really explain because words are inadequate. The easiest way to think of it is that they share in the knowledge of the angels. So while they do not have worldly years and experiences, like the angels they are aware in ways that living beings are not. It's not a bookish or "experience" awareness, but it's a knowing of how things "really are," and a share in the infinite goodness of eternal life outside of time, matter and energy (none of which exist in heaven, so souls in heaven are not "energy beings," since there is no "energy" in heaven, just as there is no matter or time). So even premature babies, aborted embryos, however short their life all gain a portion of the knowledge and awareness of angels, since, like angels, they receive all of their life sustenance from God's will and power. All that exists in heaven exists because it is within God. Thus, even the tiniest of infants who never got to live at all are not deprived of mature awareness, but it is a totally heavenly based maturity, not earthly based maturity of experience at living life.
Children do not become angels, by the way. I mean, sure, it's fine to call them God's littlest angels, but angels are spirits created by God who never lived in conditions of time or matter. Children lived, even if only a few weeks in the womb, with the soul in the body's temple. Thus the souls of humans go to heaven; they are not transformed into being angels since angels are of totally different spiritual substance, not having ever been of earth.
Further, children are greeted by their nearest relatives who have achieved heaven. Through their angelic and God given awareness, they know who everyone is, even if it is a grandfather or grandmother, even multi generational back in time. Like I said, the "nearest relatives who have achieved heaven." God will go back however far he has to, ahem. I like to think that every child has a lot of relatives in heaven and they do, but sometimes it's not of the current generations, to be bluntly honest. People who want to be reunited with their children need to understand that heaven is merited individually; having a child in heaven is not one's "meal ticket" to getting into heaven. God always hopes that people will be more open in their hearts, led by their children, into more love and belief, not less. I can tell you that many times it is the desire to see one's child again that has melted cold hearts of disbelief in their parents, their grieving families, and their caregivers. Sometimes that takes time, of course, but throughout human faith history that has been a powerful directional toward God, to think about the loving care that one's child is receiving there with God, and to yearn for reunion in time.
This is, by the way, what I tell adults who aborted their children, and who years later regret it. Do not ever lose focus on the fact that you can be with that child, and not in disgrace or recriminations or embarrassment, but as all are reunited in joy and the drying of tears in heaven. There are no grudges in heaven and certainly children remember only the joy of reunion. So do not ever make the error that Judas made, of total despair, believing that God cannot fix even such a sad situation as when he betrayed Christ: if only Judas had repented and believed! Likewise, even in abortion, have faith in God and his reality, and seek him during your life, and you can live in the hope of joyous reunion with the children you never knew.
In heaven there are not really "activities" per se, but one can think of it as the place where God knows the bliss that each soul most desires. Thus children who really crave the mothering find much mothering in heaven, and those who crave the fathering find only the goodness of fatherhood in heaven. Children who loved animals see their pets in heaven, and the other beings of heaven that are of that spirit. When Jesus tells the story of the poor man Lazarus who died in pain, neglect and poverty, Jesus points out that Lazarus is in the bosom of Abraham in heaven. Abraham is the father of all the faiths in the one God, and thus one can see an example of what I mean. The poor man Lazarus needed a father, a provider, and thus his bliss is to be cradled by the great father of all the faiths, Abraham, in heaven. So it is with children where they are surrounded and loved by whatever relatives, saints, angels and fellow souls that they could ever desire for their bliss in God's presence. They do not "miss" anyone, no matter how much they loved on earth, because there is no passage of time in heaven with which to miss anyone. It is difficult to imagine how the heavenly abode is, totally outside of the existence of time. The best way to describe it is that whoever is going to be in heaven seems to be "already there," even though there is passage of time on earth. In other words, your child does not have time to miss you, quite literally, he or she does not have the time since there is no such thing as time itself. That does not diminish the joy of when you are reunited.
That, by the way, is why the Apostles and disciples thought so much about the resurrection of the body at the end of time. It is too mind boggling for them to comprehend heaven and their existence as souls, so they focused on trying to understand what it would be like when their bodies are resurrected, all of life passes, time ends, and there is the new heavenly "Jerusalem" for those who merit it. It's not like they didn't understand that they would individually be with Jesus in heaven when each of them died, obviously. But rather than try to imagine that, they instead asked Jesus about when they would be in their resurrected bodies and all the earth would be anew. THAT they could understand and quiz Jesus about. But as Jesus reminded them, even he himself did not know when the end of time would take place, only God knows that. So Jesus reminded them that he was going to heaven to prepare places for them in heaven, explaining to them that God has many mansions (rooms) in heaven and that he, Jesus, would go ahead and prepare their places. Again, Jesus is using terms that humans can understand. It's not like God literally has little houses custom decorated to the liking of each human (sorry New Agers). What Jesus means by mansions or rooms is what I explained, that the place of one's bliss is prepared.
So when people joke that when someone dies, "God must have needed another musician," or "God needed another baseball player," etc., that is in a joking way actually closer to the truth of heaven than imagining little marble mansions or log cabins of one's own. Spirits in heaven cluster around their love relationships from earth and also their commonality of bliss. It is not so much the type of interest but the type of love that they most desire. The gravity of heaven is the love of God and it is love of God and being in his light that ennobles through and of God the relationships that one has in heaven. So just as gravity on earth keeps one steady on the planet and able to move and breathe the atmosphere that is also kept in place by gravity, God's love and presence is the gravity of heaven and all gather within heaven feeling the mutual bonds of love and bliss. Yes, there is a lot of singing in heaven because the angels constantly sing God's praise, and it is never tiresome and it never grows old (and one does not have to worry about being out of tune or not having perfect pitch ;-)
So the only comfort that I can offer grieving parents is a powerful one, but one that is forward looking as time slowly heals sufficiently so that the grief becomes bearable and life can go on. The comfort is that no matter what the circumstances of their passing, innocent children do not carry fear or pain with them, they find heaven, they know God, and they are surrounded by relatives, angels and others who provide love and bliss.
I hope that you have found this in some way helpful.