1. Grilled "Burger" night - buy one pack of veg burgers (the one the vegetarian likes) and then just plain hamburger patties and take to a grill at the resort - if they don't have a grill, pull out the pan and do it in the room (that's worse, though, b/c you can't make everyone's at once). For the diabetic, have lettuce that can act as a wrap (romaine?), and then regular buns for everyone else. Have cheese, lettuce, tomato, onion, (avocado - makes a veg burger great, and diabetic may want it), ketchup, mustard, mayo. Serve the burgers with sliced strawberries, and for those who want them, some potato chips.
2. Chili meets all-beef hot dogs night -
https://www.epicurious.com/recipes/food/views/vegetarian-black-bean-chili-230632 You can doctor this by adding whatever extra veg or bean you like, and even extra spices, but it's a good "base" and a fast and cheap cook. Have some sour cream and avocado for anyone having it as a bowl of chili, and have some cheese and onion for anyone putting it on a hot dog (you can microwave or boil the dogs tonight, b/c I'm having them for the kids, and they won't care
)...serve this with sliced watermelon and be done.
3. Deconstructed to Reconstructed Cobb or Whatever Salad night (with the kids eating the components) - Buy some rotisserie chickens, cook or buy hardboiled eggs, have some cheese, some nuts for topping (whatever non-sweetened type the adults like) and tons of vegetables and lettuces. Buy carrots shredded, buy celery diced, buy jarred roasted peppers, buy grape tomatoes, and a bag of croutons for those who love them. Rather than buying 10 different dressings, buy a single low sugar balsamic vinaigrette, and then, if someone doesn't like it, make a sweetened mustard dressing with your condo sweetener, your condo oil, and your hot dog mustard. Serve with some sliced apples, which could also go on the salad.
I've got more, but these are my top 3 that are cheap, work for 1-88, and meet everyone's needs. I would also do a baked salmon night (with a baked portbello mushroom cap for the veg), but that gets pricier...