Honestly, I agree that you should have your wedding the way you want, and it that's with no alcohol then that's the way it is. I think you should be prepared if people do leave to get some though (even if it is rude to do). If you are going to be totally fine with that (and I mean, honest to goodness fine, and won't be upset) then there isn't a problem. If there is a chance that you might be upset if people leave for a drink, you and your FI may want to consider providing a few alcoholic bevvies. It doesn't have to be copious amounts, but maybe something for a toast.