I have hit that point I think where I don't really care what people think of me not drinking. Some advice that could work for an event like that though is just fill a glass with something that looks a similar colour to a drinkie. People may just assume you are drinking. If people are invited to yours should be easy to ensure you always keep yourself topped up with something non alcoholic and perhaps no one will ask.
Personally though as I said, if people are going to be difficult about it that is their problem not mine. I have enough of my own thank you very much. lol