With a large group, the hardest part is managing EXPECTATIONS. Have a group meeting beforehand and encourage the group to be willing to split up when and if their interests differ. Set up one meal (or activity) each day that the entire group will attend, so everyone will still feel "on the same page" as everyone else even if they've been doing different things for part of a day.
We're going in May with my Dad and aunt (both over 70) and our two small children. We're generally spending the evenings together and having dinner together, but morning touring schedules are more free: the kids and I want to be in the parks at rope drop, while Dad and my aunt are more likely to want to sleep in, have some coffee or take a stroll, and then meet up with us later. They also, along with my husband, tend to be night owls who will want to do things after the kids and I have gone to bed.
To prepare them ahead, we've had a couple of family meetings to talk about Disney World in general and discuss all of our expectations for the trip. I gave everybody dining surveys to figure out where they'd like ADRs, and attractions surveys to find out what kinds of attractions (e.g., rough rollercoasters, spinning rides, elevated rides) they can and can't do. I will use that to make FP+ for the group in our "evening park" each day.
We're staying together in a 2-bedroom villa at Wilderness Lodge, so I've also made a folder to keep out in the living room each day. It has itinerary sheets for each day, which list: park hours and showtimes, dinner reservations for the whole group, generalized touring plan suggestions (Morning- MK, tour Fantasyland and Tomorrowland OR relax at the resort and take resort tour. Afternoon - Epcot, tour World Showcase with dinner ADR at Biergarten at 6:00pm), etc. Each itinerary sheet also has a "Notes" section about the day (headliner attractions in the park we're visiting, how to get there if you want to come late, what the dinner restaurant is like). There is a sheet with important phone numbers, one that gives directions to every Disney property destination from our resort (what bus or boat to take), and a separate sheet with "other things to do" that describes and gives directions to things like Downtown Disney and the mini golf courses.
My hope is that this will arm everyone with what they need to make informed choices about what they'd like to do each day, knowing that they're welcome to jump into park touring with the bulk of the gruop or to relax doing something else, knowing that we'll be having dinner and spending the evening together and can regroup then. In traveling with multiple generations in the past, we've found that this kind of flexible approach makes everybody happy, and still allows for plenty of quality time as a group.
