We didn't have that many people, but we did the vacation/reunion on a 7-day cruise to the Western Caribbean. No one had to cook or plan anything. The buzz phrase is "all inclusive" unless you go to some of the specialty restaurants on board, which would cost you about the price of dinner, they call it a "cover charge".
There was so much to do, on and off the ship; there were times when we did off shore excursions together and other times not, sometimes dinner with one bunch, lunch with another and typically we all had dinner together.
Don't say I said it, but I bet you could get a nice group discount! Planning in advance is key.
We also have done the Orlando vacation/reunion mix and match with Universal Studios/Sea World/Disney cost about the same, with the same perks, versatility for everyone. Again, planning ahead makes the vacation easy. Best wishes