I have recently become aware of the phenomenon in the USA of reports of children who claim to have visited Heaven, or had Christian visions. These accounts have no equivalent in the UK, nor have these stories and significant visibility over here - but it seems clear that there is large scale appreciation of these accounts in the USA, to judge by mass media impact and personal testimonials.
Such accounts are easy to reject, and I certainly would have rejected them when I was an atheist - unless there is a basic openness to the possibility.
If it is regarded as possible that children may be chosen as (minor) prophets - then one or more such reports may be essentially valid - and then, since child prophets are not a normal feature of Christian history, we need to make sense of the phenomenon from a perspective of God's purposes in our time.
Why might God choose children to communicate revelations?
1. One reason is that in modern society only children are open to revelation - God uses children because there is nobody else suitable. This may imply that in our faith life modern people need to be more like children.
2. Another might be that adults are more inclined to believe a child than another adult (because the child is less likely to have an 'agenda' - although his parents may).
3. Another is that the simplicity of a child's messages - which God may judge to be the kind of message that we most need. I particular, God may be telling us that we need, more than anything else, to live in hope and expectation of Heaven.
4. Another reason may be to indicate the kind of place that Heaven fundamentally is (exact details not vital) - at least to a newly-arrived visitor. I think (?) one common theme of these accounts is that Heaven a place of personal relationships, including being reunited with loved family and friends - and meeting Jesus face to face.
That's about as much as I can say from my very limited acquaintance with the genre.