This year I booked a trip for my newly combined family of 6. I found it discouraging. Disney makes it very difficult to accommodate a big family. They will not guarantee adjoining rooms, and only a very small handful of rooms even accommodate 6.
The FtWilderness cabins sleep 6, but two of those people have to share a pull out sofa, and there's only one bathroom. They are very comfortable for a family of 4. Some of the club level rooms at BWI have 2 beds plus a pull out and accommodate 6. As others have pointed out there are the 2 bedroom villas but they are limited numbers and cost prohibitive for a lot of people. I looked for months and none became available for my dates.
The new Swan Reserve has suites, but the 1 bedroom suite only has one bathroom and again, two people would have to share a pull out. It also has 2 bedroom suites but I was wary of booking that sight unseen before the hotel even opened, given the price.
In the end, we booked a deluxe family room with a connecting room at the Dolphin. You can't book those online. Both Swan and Dolphin have accommodations for bigger families, but if you look at the Disney site it will tell you that max occupancy is 4.