I think it is easier to divide into teams of two or four to cook than cook one big meal.
You need a big pot, a big stove or a big fire, lots of serving untensils etc. you need about a 5 gallon pot to cook stews, chillis and soups for 25. Maybe you good bring a grill and due some kind of bbq using real food but that is heavy. You could also just have a 5 liter pot and a powerful stove and distribute boiling water for peoples freeze dried meals