Don't be ashamed of not drinking alcohol. It is only a beverage there are plenty of alternatives. Be proud and focused on what you are trying to accomplish and enjoy eating BBQ.
Bring a 6 pack of non-alcoholic ginger beer or favorite non-alcoholic drink of choice, that way you can be assured of having a drink you enjoy.
And if it gets too difficult, check out early and get a good nights sleep and look forward to a productive Saturday.
I'm at day 69 and have been to a few such events. Once I accepted that I could have a good time without drinking, I just enjoyed the good time.