A.H.
We rent a 16 bedroom house for a week over New Years every year with a group that ranges from 30-75 people at any given time. We have been doing this for many years and have gotten more and more organized in recent years.
We have an email list that we use during the year. We designate one person in charge of food. They send email asking for volunteers for cooking each dinner, and dinner cleanup (2 separate jobs). She also writes asking about food allergies and things that people don't eat. The cooking volunteers send in recipes and she assigns each person/family one night to cook.
She prepares a shopping list that she circulates with 2-3 other people to discuss. If some people don't have children, it's good to have at least one person without children on the organizing committee to represent the views of those without kids. We add breakfast, lunch & snacking foods to the list.
One person in our group has access to a "bents and dents" store, where she shops in advance and brings food with her. When we arrive, 2 others take a mini van and go to the closest BJ's/Costco/Sams Club for most of the food. We use the local grocery store for just a few specialty things, and last minute things.
Our head coordinator collects all receipts. She creates a spreadsheet and figures out before the last day how much food costs per person and keeps track of who has paid for what. We keep a separate tab for alochol expenses. Near the end of the trip we determine how much food cost per person, per day, counting children as 1/2 people. If everyone is there essentially the whole time, it's much easier. We determine how many days each person was there and figure out their food and alcohol charges. If some people paid for food, we deduct that from what they owe (they usually get money back).
Our policy is to have 1 night with no meal organized for people to go out to eat. Otherwise, everyone pays, whether or not they were there for dinner, because we also need to cover breakfast, lunch, snacks, and we probably counted them in when we were planning how much food to buy in the first place.
Over the years, we have developed a fairly elaborate spreadsheet, that includes the cost of the rental property, sharing rooms, partial stays and a slush fund to help with the deposit.