We took a group of 23 people down in 1999. (Have I mentioned that I LOVE the Disney Vacation Club?) We had a three-bedroom villa and three two-bedroom villas at the Old Key West Resort. We had 14 adults and 9 kids, with experience ranging from "mega-veterans" (us) to first-timers.
We had two or three planned meals, and one planned group photo. Beyond that, everybody was on their own. Groups were forming and dissolving throughout each day, sometimes aided by cell phones. We had an impromptu "hey, if everybody's in the Studios, we're meeting for lunch at Pizza Planet in 45 minutes for lunch" organized by a couple of our friends via cell phones. There usually ended up being an after-hours gathering in the kitchen/living room of one of the villas (usually ours, because the 3BR has SO much room), and frequently breakfast gatherings, as well.
My bottom line: keep it simple. Don't overplan. Let groups form and re-form. Use cell phones or FRS radios to keep in touch. Plan only a couple of group activities, but that that one big group photo. And don't get too bogged down in the details to HAVE FUN!