This worked out pretty well for my daughters wedding - I know I searched the internet for advice and got conflicting information, so here goes what worked for us.
Setting - 200 guests - 180 adults, outdoors, on a hot summer night (no, not that hot summer night). Wedding at 4, dinner at 6, dancing till 10. We had an open bar - no charge.
20 cases of water - we ended with two cases left - did I say it was a hot day? We put it out in galvinized wash tubs so guests could grab one as they arrived, and placed them around the tent also. I had frozen 4 cases to help cool down the rest and save on ice.
2 half barrels of beer (actually 1 half and two quarters). We went with PBR and two micro brews - PBR went first, so don't fret serving cheap beer.
4 cases of Champagne (12 to a case, Barefoot Extra Dry) - we ended up with one left. This is the only area I think we could of gone with less - 3 cases for the toast would of been enough.
6 bottles non-alcoholic sparking cider - we should of gone more - at least 12.
7 mixed cases wine - I went overboard with the varieties - Menage et Trois red, Columbia Two Vines Merlot, Houge Chardonnay, Barefoot Moscato, Columbia Crest Riesling, Lindemans sauvignon blanc Wolersheim's Prairie Fume. The amount of wine was fine - ended up with a mixed case at the end. But if I were to do it over - I would of gone with just the Merlot, the Chardonnay, the Sauvignon blanc and the Moscato. Buy what people want - that's pretty much it - it doesn't have to be expensive - just worth drinking. And I think all of those wines are pretty good on a hot summer night
3 cases mixed soda (half diet, half regular) Interestingly enough, I should of gone another case of regular soda - we had diet left over at the end of the night, but none of the regular.
300 lbs ice - you need a lot to ice down all that, especially on a hot summer night. (no, not that hot summer night either)
We used 4 galvanized wash tubs for water, and four coolers to keep the wine cool - I also dropped some ice in the red wine cases - no one really wants to drink red wine that is 85 degrees.
The venue provided the insurance, but we still had a licensed bar tender there. Good way of making sure you are cutting off those that are getting a little too happy, and are good at dealing with people.
It was a great fun night.