It sounds like you are thinking clearly to me.
I'm sorry about your son, and you're right to step back and detach from his life right now, we can so easily follow addiction right into hell with them.
I too, would be concerned about the children. They are the innocents who have no voice in this. I had to call Children's Aid for my granddaughter, and they took her to a safe house until her mother got significant recovery again.
It's hard to do but it may save the lives of those children. Someone has to watch out for them, and I think they are lucky to have you.
Hugs