As far as planning meals go, I agree it is hard when you don’t know what they will bring. Last summer my parents, siblings & their kids and my family (over 20 of us) stayed at a house in Branson for a week. We used a Google spreadsheet and each signed up to make a complete breakfast, lunch and dinner for the whole group. That made it lots easier to plan than trying to coordinate each meal and also helped all of us ladies not feel that we spent the whole week in the kitchen. We also used the Google doc to note what kinds of other things we were bringing so we each wouldn’t have to pack so much (snack foods, extra pots and kitchen equipment, board games, lawn games, etc.).