We love Saratoga Springs (home DVC resort), especially if you can get into the Paddock. The Paddock pool has a large slide my son, who was 5 1/2 at the time, LOVED. It also has a fairly large smaller kiddie area attached. There is also a decent larger slide and a smaller kiddie slide at the main pool located nearest the Springs area.
We have also stayed at Old Key West and my son enjoyed that pool as well. Each morning, the life guards make all the kids ballon swords and put bandanas on them and they "stormed the castle" (slide), complete with the music from Pirates playing, to take it over from the other life guards and raise the Jolly Roger to offically open the pool.
Animal Kingdom was ok, but even with a savanah view room, you had to know animals daily migration schedule to see them (our area was between 4-5pm).
I've never stayed at Beach Club, but I've heard the pool is excellent.
All the villas have areas to get movies to watch in your room and activity center. You can get a schedule for the activities to be offered during your stay at check-in. We've participated once when it was raining fairly hard. My son, 3 1/2 at the time, got to make his own Mickey tie-dyed shirt. It cost $10 for the t-shirt.
Hope that helps.