It would be easier to put a little bottle of italian seasoning, for instance, in your luggage, too (I was going to say a baggie, but then I thought a baggie of oregano might look suspicious to homeland security!!!!).
I think the idea of each adult, or couple, being responsible for a meal for the group is a great one-that's what we always do when we camp with groups. I'd personally try and throw in as many healthy ingredients as possible as I know it's really easy to eat badly on vacation and I think that starts to affect our energy levels after a few days, esp if you have kids in the group.
Pasta sauce is great and easy. Buy a jar, add some sauteed veggies (always garlic and onion!) and beef, chicken, or sausage and some of your spices, if you'd like. Toss in part of the bottle of wine you've opened. Salad on the side...baby spinach, maybe. A frozen box of shredded spinach is good in the sauce. We have really like the Bertolli pasta plus noodles lately-they are part whole grain but taste like regular pasta, but have extra protein and fiber (one of my kids has to get a good dose of protein at every meal or she's a mess).
Frittata for dinner-saute a lot of veggies, like onions, garlic, bell peppers, mushrooms. Add sausage or ham. Grate some cheese (cheddar is always great) into a bowl with six or more eggs, add a little milk, salt and pepper, mix em all up. add the eggs, and stir until it's cooked through (lift the edges to let the raw egg come to the outside and cook). If you've cooked in an oven-proof pan, put under the broiler for a minute or two at the end so it's golden and bubbly on top. Serve with bread.
Spaghetti carbonara-google for a recipe, but basically egg, bacon/pancetta, cheese tossed with hot noodles so the egg cooks and forms a really yummy sauce.
Quesadillas, with a bar of fillings that people can put in theirs'-grated cheese, drained black beans, cooked ground beef or shredded chicken, black olives, salsa, green onions, cilantro, sour cream, avocado.
Ditto the above, only with baked potatoes, bacon, chili.
Frito chili! Fritos, canned chili, sour cream, avocado, shredded cheese.
My 11 year old loves to cook "buttery noodles" and kids really do like them. Cook a pot of noodles, we use elbow macaroni. Add cream cheese with chives, a chunk of butter, and stir to melt. Add a little milk, and a bunch of shredded parmesan. Salt and pepper.
Fondue would be easy and lots of fun. You can buy the packaged swiss stuff at most grocery stores and melt it in the microwave. Cubed bread, veggies, and cooked pieces of sausage, apples. Choc fondue for dessert.