Another easy idea would be to raffle off bottles of wine every 15 minutes or so. This activity is ideal for the Silent Auction hour when people are browsing around the tables or during cocktails. I wouldn't recommend it during dinner, as it would be disruptive or later in the evening when people want to dance and volunteers are wrapping things up.
Sell raffle tickets before the event and at the event itself.
Set up a table at the event with a display of some wine, the raffle box, raffle tickets for sale, and a moneybox that locks.
Coordinate volunteers to man the raffle table.
Make sure you have a P.A. system to make announcements during the event about each raffle drawing and the winners.
Try to give the each bottle away as the winners' names are called. Keep a list of the winners to give the wine prize to those who don't claim them at the event.