Been there, done that, got the tee shirt to prove it.
My first advice is don't. Okay, joking aside, at Disney, the more people in the group, the more complicated it is (and the less enjoyable, at least for me).
Somewhere like an all-inclusive is MUCH easier to do with a group. But if you are doing it, understand that some folks in the group will be Type A, and want to dictate what folks do. That's fine, unless you have TWO Type A's. Which, odds are, you will. And you'll have those that just aren't into it. That's fine too; that's why the resorts have pools (and pool bars).
I'd suggest having every family make their own resort reservations. Plan a meal or two. Plan a ride or two together. Then, plan on families to do their own thing most of the time. That's the only way it will work. I know folks want to book the same resort, but that backfired on us a few years ago. I KNEW the Boardwalk would be ideal for our large group, but someone (who had never been to Disney with their family) chose AKL instead. So we went with that. It was NOT the resort that all enjoyed (although it was okay). So in retrospect, I would have said fine you stay there, we'll stay elsewhere.
We never do rope drop, so unlike hsmamato2, that wouldn't work. We tend to get to a park about 11. I get up early at home; vacation I like to enjoy my coffee in my pj's and take my time. In my 30 visits, I've seen an opening ceremony once, and had 2 pre park opening breakfasts at BOG as well. Last time (just my youngest and me) we needed a nap by noon.
There is no way to candy coat it; large groups at Disney are WORK. I'd suggest at MOST one meal a day, but split between table service and meeting for snacks and drinks.
I've led several. One time it was my job, so I took it as that (hosted my folks and 7 others, families from Japan who were my dad's business associates, so this was a business thing that I arranged). Other times were family things. Never again.