I have 21 years sobriety.
The son needs to make the choice to go or not. The family is not obligated to do differant then usual because of one, in my opinion. I went to drinking events shortly after I got out of rehab. I did fine because I chose to. I do remember my then mother in law jumping between me and someone who asked me if I wanted a drink, she said "NO". I think she figured I couldn't say no. I did and still do. If the son can't say no now, then he needs to go elsewhere until he can.
I think a family setting is a good starting place for getting back into the real world. He and only he controls what goes in his mouth. Best of luck to him. He can do it.