I'd book 3+ units at Vistana or similar resort. It's a bit more carefree than vacation homes; you can get daily housekeeping, with that many people there's bound to be some resentment about people doing their share of the chores - and there are chores at a vacation home. With a large group 3 units that sleep 8 is the minimum; click the sponsor link at the top for pricing, Vistana will run about $1000 per unit for the week.
This kind of arrangement allows for a lot more flexibility and privacy. Perhaps some of the more solitary members of the crew would prefer to get a single bed or studio unit and have a bit of privacy when needed. It also allows different age groups to hang out at different pools so they can have a bit of space.