I would really vote for cluing in your waiter/server, or having your husband get you vodka sodas sans vodka, and then holding a glass of wine that your husband takes sips from. This has been working for me, and, especially once people start drinking, they really stop paying attention to you if they assume you're drinking, too. Also, my server kept smiling at me like I had just told her the best secret in the world
The reason I say this is because we went to a wedding a couple of weeks ago, and a. my husband really didn't like the idea of trying to be that slick with so many people, and b. I drove instead of us taking a cab, which we usually would have done, so I had to seem somewhat sober at the end of the night, so we said I was taking medicine and couldn't drink. Well, this went over like a lead balloon. It took about 5 minutes for one of my friends to call me out in front of a bunch of other people saying, "are you really on antibiotics, or just pregnant and trying to make an excuse?" And, as people kept drinking, the questions kept coming. I flat out told them, no, I was not pregnant, just couldn't drink because of the medicine, and even took pills after dinner (progesterone), hoping they'd lay off, and it didn't help. Maybe I just have asshole friends, which is another issue, but it made me SO much more uncomfortable than the times I've faked it with soda water or a glass of wine in front of me.
Obviously it depends on how big of a drinker you were before, how close of friends they are (I find that the closer they are, the worse it is because they feel more comfortable saying something or like you should be telling them anyway), and what their attitudes are like, but I just wanted to share my experience going a couple of different routes.
Good luck and happy birthday!