Wedding Reception Help Needed

My reception is 9/27/08. We are serving Sangria, Beer, and white wine on a host bar in addition to non-alcoholic beverages. We have 85 adult guests. Can anyone help me figure out how much to buy? My best guess right now is to get 1 case of white wine, make 8-10 gallons of Sangria (home-made), and have 1 full keg of beer. My fear is to not have enough but it`s hard to gauge what guests will drink the most of so do I get enough for everyone to have one of everything or how do I figure this out? Help?