That is a big group and any room that would fit everyone would be expensive. You would need a two bedroom villa at one of the Home away From Home Resorts.
They have these villas at the Beach Club, Boardwalk, and Wilderness Lodge (about 550-1000 per night plus tax, depending on when you go). They are also available at Saratoga Springs and Old Key West (approx. 480-780 per night plus tax, depending on when you go).
Your best bet would probably be to get two rooms at another resort. If you get them connecting, you will almost feel like you are in the same room. We did that when we went with some friends because the villas were just too expensive.