Well the party was a disaster. Half the people were so offended at being invited during dinner hours that they boycotted the event. Those who attended were driven into a starvation-fueled attack of other diners' plates. Carnage and mayhem ensued.
Just kidding! It was great!
About 20 of the 25 who RSVP'd attended. DH and I arrived early so we had time to make sure that our waitress understood the plan (I had confirmed with someone but wanted to make sure the info traveled to our server), and to order the food and drinks so it arrived as our guests did.
We placed our first order of food (that I outlined previously - swapping out a veggie-friendly mushroom appetizer for chicken dip) and it arrived in a timely manner. The waitress kept pitchers of beer coming throughout the night.
People ate the food but we never had to place another order! (And the food was good - people just didn't consume mass quantities.) I watched the food pretty closely so I could reorder in a timely manner. But we still had a little left at the end of the evening. It seemed that our guests were cool with the "beer and munchies" concept and mostly just drank beer and sampled the fare.
In the end we bought 10 pitchers for the group (and a three glasses of wine for a friend who doesn't do brew) and the appetizers and came in way under budget.
Thank you for your help. It was interesting to see so many different perspectives.
(edited because I hit "post" too soon!)