TNyman, I have a business trip this week also. Tuesday night will be a dinner. Last time I was out with these folks, hardly anyone drank. No one batted an eye when I ordered water. I think we alcoholics think everyone else cares what we drink. So far, I haven't found anyone who seems concerned that I don't drink. You might be surprised at the lack of reaction. However, if people really want to know why you're not drinking - I would use the"medication" line.
Best of luck to you!