I don't think anyone has mentioned Redwood Creek Challenge Trail in DCA--underrated in my opinion. It's worth checking out and if your son enjoys being active he can burn off some energy there. Another unique thing at DCA are the cats that live there...if you're fans of cats you can almost always see Snickers in the foliage near Grizzly River, across from Soarin', and another that can often be spotted way up on the rocks of Grizzly Peak by the waterfall.
On the flip side of burning off energy, they built the opposite into ToonTown--a quiet, shaded spot to relax and "come down" from all the stimulation. DL looks small compared to WDW but they really pack a lot in! I'm a frequent visitor to both, a huge parks enthusiast and I walk more in a day at DL/DCA than I do at WDW. Enjoy!