Hi Nealy!
My 5 year old's favorite resort is the Animal Kingdom Lodge. The theming is incredible and there are animals everywhere. The resort has great dining options; Boma is a great family buffet and Jiko is great for adults looking for a quiet romantic evening. There are a lot of activities for young guests at the resort and the pool is fantastic.
His second favorite resort is the Beach Club. It is located on a lake between Epcot and Hollywood Studios. They love Stormalong Bay, the main pool that is shared between the Beach Club and the Yacht Club resorts. Stormalong Bay is a spectacular sand-bottom pool. My 5 year old could spend an entire vacation in Stormalong Bay. The Beach Club is only a 5 minute walk to the International Gateway of Epcot, providing easy access to the theme park and all of the great dining choices in World Showcase. My children also enjoying visiting Disney's Boardwalk at night which is across the lake.
With young children, you might be spending a lot of time in the Magic Kingdom (MK) and thus should consider a MK resort. That would make it very easy to return to your room for a break, swim in the pool, nap, etc. The Contemporary, Polynesian, and Grand Floridian are on the monorail while the Wilderness Lodge has a boat to the theme park. The Polynesian and Wilderness Lodge come to mind when I think about young children.
If you are looking for less expensive options, then I recommend Port Orleans Riverside and the Caribbean Beach Resort. Both have a lot of activities for children and have very nice pools.
Here are some other
opinions about planning a first trip and my thoughts on bringing
young children. Write back if you have any more questions!