Or, you could consider renting points and staying at DVC...there, the number of points needed to stay (and the price per point you negotiate with the owner you rent from) doesn't vary with the number of people in the villa...plus, you don't pay tax, either; plus, DVC provides free laundry (in the villa except for studios, and studio guests use laundry facilities located near the pools, w/out charge (except for laundry soap if you don't bring your own)...between tax and extra adult surcharges, this might be the way to go...
A DVC studio (OKW, SSR, BLT, AKV, VWL, BCV, BWV) sleeps four (a queen size bed and a pull-out sleeper sofa, except at OKW where it's 2 queen size beds)
A one-bedroom sleeps four, too (but you get a full kitchen, in-villa laundry, and a 'living room' w/a pull-out sleeper sofa along w/a bedroom w/a king sized bed...jacuzzi tub in the bathroom, too!
A two-bedroom sleeps 8
A grand villa sleeps 12
(Some of the resorts also have a sleeper chair which adds one more to their occupancy possibilities)...
Renting has its own "issues," so if you want to explore it I'd recommend hopping on over to the DVC boards and reading some of the MANY threads on the topic over there...there's no "set price" to rent...but the range seems to be $10-$12/point...point "costs" for a villa vary widely, too--but expect a low of 10 points/night for a studio at OKW to a high of 33 points/night for a Magic Kingdom view studio at Bay Lake Towers...
Good luck!