I think it is awesome that your son felt comfortable enough to come talk to you about something like that. I also think it awesome that you are taking action by taking him to a psychiatrist.
In one rehab I was at, they made us write a list titled "100 things to do instead of drugs" - I suppose you could substitute the word drink for drugs. When I was going to relapse, it was just going to happen and no list could help. But if I had even a minute control over myself, I found that my list did help somewhat.
I hope that helped...