Hi to everyone and OP - First, RMHC is always grateful for donations and volunteer support. RMHC relies on a network of well over 30,000 volunteers to help keep the Ronald McDonald House programs running every year. Without the volunteers, we simply couldn't do what we do everyday.
Let me say, I work for Ronald McDonald House Charities in Illinois. There are actually a couple of rules that we really adhere to with respect to meals. First, meals must be prepared in the Ronald McDonald House kitchen. The reason revolves around food safety. Simply put, we don't know what someone's kitchen at home looks like and, more importantly, how long something was in someone's car. The only exception is, as someone pointed out, food that comes from a commercial kitchen setting (local bakery for example). It would be all too easy for something to go bad in a trunk or something. This included pre-cooked food at home (e.g. pot pie, chicken, etc. doesn't meet the safety standards).
Second, please try and keep things separate. As someone else pointed out, there could be nut allergies, seafood/shellfish allergies, etc. or just vegan/vegetarians and we want everyone to try and eat when possible. You are correct, that not everyone eats at the same time, so things that reheat easily are always appreciated.
Single serve items (e.g., pretzels) are always appreciated as snack items too. Usually, the different RMH programs will have wish-lists posted online for these items. Each program needs something different just based on what is in their pantry.
In terms of breaking up the girls, 5 or 6 could work on a taco bar (great idea!), a couple on a salad, some on pasta, some on dessert, etc. One thing that is very helpful for dessert items (for example), is to put single brownies or two or three cookies in individual baggies when cooked and cool. Due to the flu, we are trying to keep individual house guests from "reaching in" to a community plate setting right now. Guest families don't think about it - until they see how it's done. Then they apprciate it.
Thanks again for agreeing to do this. It should be a great experience. We really appreciate the help. If you (or anyone) has additional questions, post here and I'll check and respond.