[Morrigoon]

Nephy, I think your relationship with your son has come a VERY long way when you are able to handle this as well as you have.

Only you can decide if you are going to allow it in your house. But FWIW, there can be some distinct advantages to knowing where and when he's doing it. (Being that you have more ability to control the where, when, and how)

If you would like to consider allowing it, you can lay some ground rules for him, like the following:
1. Never when anybody else is home - anybody. Especially the other kids.
2. Protection MUST be used every time, all the time. It is to be disposed of properly.
3. He must wash his linens afterward.
4. No telling his siblings about your arrangement. As far as any of them know they'd better wait till they are 18, and you expect his support in that.

This will help him develop a sense of how to go about his private business responsibly and appropriately.