I didn't see a need to announce my sobriety publicly to anyone, even my non-immediate family. Over time what I found was that for the most part no one really notices one way or the other anyway. As alcoholics we tend to obsess about what other people think about our drinking ( or our abstinence ), but the reality is that they really don't think about it at all.
I told my wife and my immediate family but other than that I dind't feel a need to tell anyone else. And thusfar I've never even once had a question from anyone about why I wasn't drinking. Sure I've been offered a drink but I just ask for a water or a soda and that's pretty much the end of the conversation.