It’s best not to begin with Adam and Eve. Original sin is baffling. Besides, kids are scared of naked people holding apples. Start with the talking snake. Kids like animals. Children like what animals have to say. Let him hiss for a while. They’ll figure him out in the end. Describe sin as suffering and leave it at that. Steer clear of confessionals. Children associate them with toilets. They’ll be able to describe it soon enough. If they feel the need to apologize, tell them the moon is there to forgive. As for the priest, let him sleep. He’s less dangerous that way.