Hi SG, it's good that you have a chance to make a "plan" before this potential work event. There have been lots of posts in SR about this topic, and it really comes down to you and what you are comfortable with sharing. What you shouldn't be worried about is the fact of you not drinking being the latest gossip topic at work. We Alcoholics are hyper aware of who's drinking and who isn't, but normal folk don't really pay much attention. Because drinking isn't an issue! If you are really concerned, you can give an excuse of "I'm driving later" or "I'm on antibiotics" or "I'm on a diet" etc. either way I'm sure it won't be a big deal to others but it is a good idea to have a plan.
Amp and Inc, I feel for you!! Feeling depressed is the worst. Try and take things slow, the quote "easy does it" always helps me. Know that the bad feelings will pass, they are just a part of us being human. Sending positive thoughts your way.