To keep everyone together at an on-property resort, your only options would be a 2-bedroom villa at OKW, AKV or BLT, or a grand villa at any DVC resort.
To give you an idea of pricing, using AKV as an example, a two bedroom villa in October would range from about $900-1100/night. You would need to add resort tax of around 12%.
A grand villa would range from $1800-$2000/night, plus resort tax.
Renting from a DVC owner would significantly reduce the cost, but you'd need to book well in advance. 7-11 months out for a two bedroom, 11 months for a grand villa. And you would need to assume that you would not get your money back if you need to cancel.
You can, of course, split everyone up into multiple rooms, but be aware that Disney will not guarantee connecting rooms.
You'll do better price-wise offsite; check out our Orlando Hotels and Attractions board for lots of info on your offsite choices.