OP,
I think I've mentioned to you before, but I am getting married at Mandalay Bay next week.
Ceremony is at 5pm. We're providing a shuttle to take our guests to dinner at a restaurant. They'll have cocktail hour at 6pm and then dinner is at 7pm. During the cocktail hour, DFi and I will go around with a photographer and take pics at the Vegas sign and wherever else we can go in that time.
We're doing a consumption bar and will pay for the drinks.
I figure, with a group of around 25 of us, dinner will take 2 hours at least. After dinner, whomever is still awake is welcome to join us in the lounge. We'll probably start a new tab then.
I think if you buy a couple of bottles of wine for your table, they should be fine. But it may be awkward when you tell them they can only have one drink.
FYI to those being dismissive of the buffet, Mandalay is not your typical buffet. They have very fresh food, tons of variety, etc. Just saw it featured on some show on the travel channel. It's not cheap either.
ETA:
We went to a destination wedding in Puerto Rico. They served only beer and sangria. There was a bar outside the room wwe were in so when anyone wanted something else, we went out and got some. Only minor rumbles, but no one was really miffed.