Sounds like you will have your own transportation...or maybe you should. You can get out on your own if need be. And like you said, leave early if need be.
I'm weird (I know, hard to believe) but I don't have a huge problem not drinking at big drinking events. I have to be careful about what happens after. It hasn't happened in a long time but I have relapsed after returning home from stressful trips of trips that involved a lot of booze. Weird.
Have a plan. You'll be fine. And have fun!!