Fear of flying can be very successfully treated with cognitive behavior therapy and other methods. I used to be quite afraid, and am not any more.
I don't think your alcoholism is much of a factor. I drank flying, and I took xanax flying, and I did both. Personally, I think it's the alcoholism in you that's telling you (and has told you in the past) that you can only fly drunk.
If you aren't 100% committed to maintaining your sobriety through flying and for the rest of the vacation, or 100% sure you'll *stay* 100% committed, I advise you to cancel it. Take a train somewhere nice. Your situation is not a good reason to drink, imo.