If I was in that situation, I would tell the kid what I believe in, that there will be an after-life. But, I would also say that not everybody believes in it, and nobody is exactly sure what happens. Besides that would be the truth, nobody knows what truly happens when we die, there is no proof to support either claim. It is all opinion until someone dies, then they get to see what happens.
Edit: Oh yeah, why is this not in the politics and religion forum. We really need some kind of automated system that moves threads like this the appropriate forum, because obviously only a select few of people no that threads like these will get people talking about religion.