Hi Estelle,
With 8 people in your party, I recommend staying in a
Disney Deluxe Villa. A two bedroom villa should be large enough since there is typically also a sleeper sofa in the living room, depending on your exact sleeping arrangements. Three bedroom villas are also available. Besides having more space, a villa also offers a fully-equipped kitchen and washer and dryer.
Since you are spending the majority of your time at the Magic Kingdom, you should consider staying at Bay Lake Tower at Disney's Contemporary Resort or the Villas at Disney's Wilderness Lodge. These are Disney Vacation Club (DVC) properties, but you do not have to be a DVC member to stay there. My family loves the Villas at Disney's Wilderness Lodge. In the Epcot area, we've stayed at the Beach Club Villas; it provides easy access to Epcot and the pool there, Stormalong Bay, is absolutely amazing. I think it is simply the best pool area on property.
Besides staying in a Deluxe Villa, you should also consider staying in two connecting rooms. That's worked out well for some of my travels in the past. Just keep in mind that there is no guarantee that you will get connecting rooms.
With 8 people in your party, you might be interested in some of the Grand Gathering options available to experience at Walt Disney World. For more information, call (407) 934-7639.