I agree that it should be his choice, but in all honesty, he probably doesn't know what he needs as far as treatment at this point. HE probably thinks he needs very little treatment, can "do it on my own" kind of thing. There are people he can see, intake people, or doctors who deal with addiction (addictionologists) who, if he is HONEST, can guide him as to what kind and what length of treatment he needs. Just be prepared...usually, the longer treatment IS better. We addicts are usually in pretty strong denial of our problem and it takes a while to get through that.
He is perfectly capable of making all the phone calls, appointments and decisions without any help from you or his parents, just as you said. Yes, you will be left at home with all the responsibility but if his addiction progresses, I promise you, that's what's the likely outcome anyway as he may be there physically, but he will be high more and more or he will just start not coming home for periods of time.
Hugs and prayers!
Amy