Here's what I did(and learned) from our April trip with 16 family members... First, talk to your group,ask them how much input they want in the daily FP plans (we didn't plan dining much together) My group was good with me making FP plans for us all. SO I 'friended' all their
MDE accts,so I had access to the tickets at 60 days. Then I booked FP from toughest to get (1st) to easiest to get (last) I also familiarized myself with rider swap,since we had 3 kids 5 and younger. Using FP+ and Rider Swap enabled me to plan at least one ride pp on our group plans, and frequently left 'extra' rides for whomever wanted to use them after our group time block. (my nephew rode Pandora 5 times that week) Originally I had planned a 'block' of 3 FP for us all,between rope drop and about noon. This turned out to be a little ambitious IRL, b/c I hadn't calculated the extra time we took with such a large group,and swapping out. So if our FP were about one each hour, it took us that FULL hour to get it all done.FP wise. This made for a problem I hadn't foreseen, one family in our group had 3 kiddos,and they packed a lunch daily.... between rides 2&3 daily,they'd kind of want to stop and relax with some lunch but b/c of the FP,we had to plow on and finish our times. Not terrible, but not as relaxing as it could have been. In retrospect, I would have made FP3 for 2 hours after FP2,so a plan of 9:30,10:30,and 12:30 (break for lunch at 11:30) would have been smarter than my 9:30,10:30,11:30 schedule.
AND after our initial 3 hours together, everyone was free to go and do what they wanted. At times this got a bit confusing,and we wasted a bit of time here and there 'figuring' out groups etc for afternoons.... but overall, we all packed our patience for such things,and it was fine. SOme afternoons some of our group stayed together,sometimes we all broke off separately,depending on our moods. I admit it was a challenge when I booked 2 HS days,and one family didn't want to return to HS that 2nd day (I don't blame them, it wasn;t much to see or do) but we all adapted plans to accomodate them. (so that fam went to AK instead,some in our group forefeited HS FP+ and went to Epcot on a whim,and the rest of us went to HS as planned.) It all worked fine. I enjoyed meeting daily each morning,and we all spent time together in the pools over our week also.
AND most in my group didn't understand fully FP+ OR rider swap. So for that 3 hours ,I 'took over' the ticket options,and told each sub group within our big group who was riding what,and with whom. (i.e,16 people, parents set 1 gets RS for baby,parents set 2 gets RS for baby, then group 1 within our 16 uses FP to ride,then when they're off, group 2 rides,and any who didn't ride before,or want another ride (we're talking a bunch of littles here!) can use RS to get on the ride. (this worked well b/c one fam member bought his ticket about 5 days before we traveled.

So to sum up, I got 'control' of FP+ plans. I planned a 3 hour block daily for together time,in which I held the tickets and called the groups. (whew) then after our 3rd ride,we all did whatever.(we needed it!) My DSIS planned a few meals with those in our group who wanted TS,and we planned those times/places around the FP+ plans.
It can be done, and we all had a great time in spite of sometimes needing to exercise patience with one another.... honestly, when things got touchy, that was a good time to go swimming!