This is a topic near & dear to many Sacred Harp singers who dare to cross the Mason Dixon line (in either direction) to sing.
"All day singing with dinner on the ground" in Alabama or Georgia can often mean "Huge spread of high fat food with all day singing." People are famous for thier fried chicken liver, bar-b-que beef, peach cobbler or red velvet cake. There are usually huge platters of ham & cooked vegetables frequently are cooked with a little pork fat for seasoning. Frequently found as well is the visting northerner with 3 things on their plate, carefully inspecting the dishes, in hopes of finding something that is meat free, and being urged by a generous but now slightly insulted cook to try to dressing, etc. The dessert table is a really safe bet.
Attending one of these events to the north, especially in Vermont, the reverse is often the case. I recall one event that was not really terrible large with at 3-4 spicy peanut noodle dishes. One was mine. Another time one where hardly any meat was to be found. Southerners who came to some of the first northern singings 10-15 years ago say they went home telling their friends all they had was macaroni & cheese. They didn't even know to call it pasta salad. Organizers of events well attended by southern guests have learned that at least a few have to bring the meat dishes. There are also often segregated serving tables-meat here--meatless there or small ingredient lists next to the bowls.
In reality, though, discussions of different food ways can be a good ice breaker. That is how I've heard about the reactions to the food. It's also wonderful to join together in the singing square; ominvores, carnivores & vegitarians lifting our voices in joyous song. If you can sing, no one cares what you eat.