My wife is a moderate JW, me I am agnostic. She can "offer" eternal life on earth, which is difficult to top. First I told him, that there is actually no proof for what his mother tells him. And that many different people (me, his grandma, his muslim friends) believe many different things about what happens after we die. But nobody can prove it. I think he gets that. But if it is a question of belief, he might think of choosing to believe the most attractive option. My son wishes he will never die. I can tell him things like there won't be enough space on the planet, if people keep having babies. Or that although we die, we keep on living in the memories of the people whe cared about us. But that's just dry bread compared to all the sugar and cream his mother can offer him.
Any suggestions what else I could tell him?