Please see the post (thread) by Isaiah today in this forum Not a demon...
If you take it to heart, I believe it will give you the strength to say no. No excuses necessary, just the truth. You're not drinking anymore. If they seem offended, you can ask them why. Then its their turn for excuses. Yes their behaviour will be disrupted, theyr'e used to drinking with you, you are enabling each other to drink, its a social thing. Perhaps there are other ways they could be offended, of which I know not.
If I'm not wrong about CBT, if you drink it means you want to drink. I understand you don't want to ruffle feathers, but to do what you know is right for you (in this case in no way selfish), you might step on some toes.
Your CBT might be proud of you, I will.