It's been discussed before so I will just give you a gentle reminder. Kids don't like this kind of sh*t. They just DON"T. Its very uncomfortable. I can remember a spot in my teen years where my there was a lot of tension between my folks and we all picked up on it even though there were no arguments. I wondered if they were getting divorced or what was going on. Its a queazy feeling. I think if they had tried to tell me what their issues were I would have vomited on them. I did not want to know, its above the pay grade of a teen to understand the dynamics of issues in parents marriage.
What I do know (having been one) is kids generally do know a hell of a lot more than we think they do. Perhaps your son has seen the information on the Rehabs. Who knows. I'd just give him his space to be. What will be regarding wife and her treatment will be revealed in the next couple of weeks. At that time you can decide what he needs to know if anything.
I know (LOL) that you most likely will not agree with what I am going to say - but I have to say it. Please allow your wife some control in her life and accountability to handle this situation. If she is unwilling to make an appt to visit one of these centers of her own accord your doing so for her is not helping this situation. I don't care if its her nature to drag her feet. She clearly doesn't drag her feet in making sure there is alcohol in the house. If she can buy a bottle she can also pick up the phone and make an appt. You can not MAKE her get sober.