You can't go wrong with a timeshare resort that's associated with a hotel brand name. They're generally among the resorts that are kept up the best and offer a higher level of vacation experience. Of course, there are other area timeshare resorts that are very nice, too.
The three Marriott timeshare resorts at the Marriott World Center are the closest Interval traders to the Disney theme parks - Sabal Palms, Royal Palms and Imperial Palm Villas are resorts. The PP mentioned the Sheraton Vistana Resort, which is just around the corner from the Marriotts at the World Center, and that's a very large resort with a lot of amenities and activity. Most of the villas there have been refurbished in the past couple of years and are right up to date.
A little further away, but still very close to Disney and other Orlando attractions, are Sheraton's Vistana Villages. Smaller than the older, sister Vistana Resort but offers the same type of activities and amenities. I think Villages is a high quality resort and we like it a bit better than Vistana Resort.
In the same general area - near SeaWorld/lower International Drive - are three other Marriott resorts. Cypress Harbour and Harbour Lake resorts are on Westwood Boulevard (across the street from one another). Cypress Harbour is, IMO, the nicer of the two but Harbour Lake has a big following particularly so from families with young children because of the pirate ship water feature but the villa furnishings aren't quite as nice as those at Cypress Harbour or Grande Vista. Grande Vista is located a mile or two from the other two, just off International Drive. It's the largest of the three and has been undergoing refurbishment to update the villas.
I think, if you're looking for high quality in terms of villas and amenities, that it's difficult to beat a Marriott and either Cypress Harbour or Grande Vista would be great choices. But the two Sheraton Vistanas would be solid choices, too. If the ship water feature is something that would resonate with children in your group then Vistana Villages or Marriott's Harbour Lake would do the trick.
One other Interval trader that I'd consider is Cypress Pointe Resort (there are two, adjacent resorts using the Cypress Pointe name - the "Resort" has been refurbished making it the better choice, while the "Grand Villas" section is either just beginning or about to begin it's upgrading). Cypress Pointe is located about a mile and a half from Downtown Disney. It's a nice resort, that's in terrific condition and has a great location.
Dick Taylor