Congratulations on 5 weeks, digitalcomfort.
My experience (and I am only on 11 weeks) is that most people around us know that we have a problem with alcohol. We try to hide it but they know anyway. So, in general, my friends have been relieved when I have said that I wanted to avoid alcohol because it had been getting on top of me. There is the odd one who doesn't like the idea that I am sober but then that reflects more on them than on me.
You don't even need a range of excuses actually. It is easier to just say "No, thank you" and that's it. No explanation required.
I have even been congratulated for setting a good example. And they love having a sober driver around too!