I'm not an atheist but there is no life after death
That death is when you are no longer living
I will teach him and explain everything about death, god, religion, etc. He can choose what he wants to believe when he is ready
I raised my son with buddhist philosophy. When he was little, he would tell kids being mean, that they were going to come back as bugs. Always made me chuckle.
It happens to everyone.
Death is death. You die and nothing else happens.