I would like to present some specific ideas about Sleeping Sex mechanism.
1. son sneaking into mother room at night or sharing a bed with mother.
2. son rubbing mother body and slowly taking off she clothes and touching mother chest and pussy or ass in while mother sleeping. (licking mother nipple also be good)
3. son insert penis into sleeping mother pussy, and she kept pretending sleep until finish cum
I hope these can be interacted depending on the level of relationship with son