I am not a professional but I am one of those go to people for various events. I camp with a group of friends every year. There are 60 of us and we set up a one kitchen and group hang out spot.
Here is a list of some of the equipment that has come in very handy for this camping trip and my big fat wedding and other parties. These items are owned by various different friends and we lend stuff to each other as needed.
Propane burners and tanks. We set up 2 propane grills and a 2 burner stove top to cook on. We bring extra 5 gallon tanks.
Several of the really big 5 day coolers.
10' by 10' pop up canopies. Most of the families have 1 or 2 of them. We pool them and bring 8 or so on the camping trip.
Several large stock pots that are 4 to 6 gallon size. They are great for making beer, canning, heating water to wash dishes, and feeding large groups of people.
Some sort of griddle surface. cast iron or a propane griddle top stove
Long handled ladles, serving spoons, spatulas and tongs. Stainless steel holds up really well.
Giant serving bowls are great to have for prep and serving
Chaffing dish frames, aluminum trays and Sterno cans. I bought them for my wedding and have used them several times a year since. Tongs and serving spoons
Plastic cutting mats and a set of cooking knives you are not worried about someone else abusing.
lots of paper goods. cups, bowls, flatware, plates, napkins and paper towels. Ideally stuff that is easy to burn.
If you have some power running several coffee machines at once is faster than waiting for a percolator style coffee maker to make coffee.
Trash cans and liners. We also have buckets for waste to be composted. This is real easy during prep.
Shelving is real handy when you are cooking for a bunch of people. The plastic ones that come apart are real handy to get stuff off the ground.
Have extra tea, sugar, salt, pepper, spices and condiments if possible.
Lots of dish detergent! You will surprised how much you go through after a couple of meals with disposable dishes.
Two large bins to wash and rinse the dishes in. We use 2 storage bins for washing dishes. The one for the hot water gets some cold water in the bottom before the hot water is added. Large towels make a good drip tray.
Have a sign up list for people to do chores to help. Also have a donation jar with a note for things you are looking for set up. Some people may be able to help and it will send a message for others to pitch in and help.
I will add more to the list as I think about it