If he's willing to explore therapy, I'd recommend a more holistic or generalized approach, if he's asking for your recommendations of course. Yes, he has a mom that drinks, at the same time the focus needs to be on himself and any types of behaviors that are troublesome to himself. The other *aha* moments will eventually fall into place.
I'm trying to think how to explain this. I, personally as an adult, returned back to therapy wanting to work on my anxiety types of reactions-catastrophizing, learning boundaries etc despite knowing that I was struggling with my marriage and also wanting to adjust things in my relationship with my mom. One skill built upon the other. Then I could step back and see where my reactions/feelings/emotiins etc were coming from.