My cousin got married and didn't serve alcohol and though the reception was held at a restaurant with a bar, they didn't even allow people to bring purchased drinks into the reception room.
I respect their choice, but it was the quietest and boring reception I've ever attended. Most of the guests (especially the older people) spent a good amount of time out of the reception room and huddled in the restaurant's bar area. It didn't help that the bride was mean and testy during the entire thing.
If I was getting married and didn't drink and NO ONE invited didn't drink, that's a different story, but for the guest's sake, at least have a pay-your-own way bar area or provide wine and a champagne toast.