It is really difficult and not a good sign if he is defensive. Not drinking however has to be a fundamental plank of all round sobriety. Everyone around him has to be made to understand this. You can only do so much however, it really is up to him to come clean with his family and friends and explain that he cannot and must not drink.
If he can’t do that, then if I were you, I might be inclined to think about my own position and whether you can continue to support him in his recovery or whether you should leave. I say this from experience – my own husband refused to countenance the idea of not drinking alcohol until recently, by which time the damage to our relationship was more or less done.
Good luck and I hope your holiday is restful and enjoyable.