Atheists: What would you say to a dying child who asks you if they'll go to heaven?

[Crossless2.0]

I'd lie to him/her and say "Yes, you're going to Heaven." Because theists have made that acceptable.

Atheists agree there's no good reason to believe that there's a Heaven. But this is different from proving there's no Heaven. So, going to Heaven is a real possibility.

Am I wrong?

No, you're not wrong. Not believing in unevidenced claims is not the same as proving the claim untrue.

That said, for me, the 'possibility' of such a thing being true pales in comparison with the 100%, rock-solid fact that people often believe things that bring them comfort, no matter how outlandish the claim.