Hello fellow Codie!
I understand your conflict, but first and foremost you need to think about you. While this may sound selfish, you are talking about your livelihood, your career. You will need that with or without him, right?
I'm new to this too, and it's been an emotional roller coaster. Part of axing the Codie in yourself is to put the responsibility and the consequences of his drinking on him. You can fix him, you can't cure him, and you're certainly not responsible for his idiocy. Of course, since he isn't in any kind of recovery, if you don't give him a heads up, he is going to see it as a betrayal within your marriage. Don't let him use that on you. He needs to man up, so to speak, and accept that he and his addiction have gotten him into this situation. Ultimately, it's your choice, but I'd saying if you wanted to break the Codie cycle, don't tell him and let the chips fall where they may because they are going to anyway. The talk is going to happen whether you tell him it's going to or not, so it's out of your control either way.
I would also have a talk with your boss as well and explain that he/she needs to address everything to do with him, or you for that matter, just for what it is...a work situation. While they were probably just trying to give you a heads up so that you could prepare, it also puts you in a tough position. Your carreer versus your marriage. This way you can honestly say that you didn't know.
As far as the Christmas party goes, tell them to stuff it because you're not responsible for his actions. Telling you not to bring him if he's drunk was wrong. He is not your child, so don't blame yourself one little bit
*Hugs* sweetie. I feel your pain...and frustration.