I agree with Kimberle. If I were 4, I'd sleep in a cardboard box if I could go to Disney World when I woke up. I think the resort choice needs to be the one that is most convenient for the parents. My 4 year old loved our stay this summer at the Swan, which is not considered a kid oriented resort. He keeps asking to go back to the "hotel," not WDW, but the Swan. The Swan/Dolphin location is so good that we could go to the parks for just a couple of hours at a time. It was so easy to go back and forth from the parks to the hotel, and a well-rested 4 year old is a happy 4 year old. You save a lot of time of travel time.
I would choose either a monorail resort or an Epcot area resort for the location. Contemporary would be cool because of the monorail going through the hotel. Poly sounds like fun for all ages. BW has a fun playground, the clown pool, and a community room. I love the Epcot area resorts so I can walk to Epcot and take a short boat ride to MGM. My kids think the boat is another park ride. Like I said, Swan/Dolphin is where we stay because of the location and their discounts make them more affordable than the other deluxes. The grotto pool and play ground at S/D are both great too. Our bus service from the Swan to the MK was excellent this summer. The bus went directly to the park after picking up at the Dolphin.
I stay away from the value and moderate resorts because of the how spread out they are and the long waits for the busses. We didn't rent a car at all, so that helped offset the higher cost at the swan. My son saw a picture of the giant Play dough at All Stars and said he wanted to go there. We went to the Honey I Shrunk the Kids playground at MGM where they have a giant playdough can and he never asked to go to All Stars again.
If you haven't done so already, look at allearsnet.com for pictures of the resorts. Disboard also has a section where people rate and review the resorts.