Hi, Claire! The latest promotional offers can be found right on the
Official Walt Disney World website. You can see the latest offers, which currently include room discounts or free dining.
As far as accommodations, there are family suites, which will sleep up to six guests, at the Art of Animation Resort or the All Star Music Resort. You'll also find cabins at Fort Wilderness that will sleep six people as well. The Disney Vacation Club properties have suites that will accommodate up to 12 guests, and those have full kitchens, washers and dryers in the unit, and a very luxury feel. You don't have to be a DVC member to book a room at those resorts.
With a group this size, you'll want to book things as early as you can. Try to get your dining reservations booked as close to your 180 day window as you can to secure the experiences you really want. Booking your rooms early will help ensure the choices you'd prefer as well, so as soon as your dates are locked down, get the ball rolling!
I've traveled with extended family, and we tend to split up for part of the day, but always regroup for dinner. That allows those who are more interested in thrill rides to do their thing, the ones with little kids can focus on their entertainment, then we all get back together at dinner to share the day.
If we can be of any help during your planning, just come on back and let us know!
Happy planning!