Unfortunately, Disney Springs is mostly shops and restaurants, like a large outdoor mall, where you would have to "run through the raindrops" to get from place to place. DD14 and I had to do this in Nov., as we stopped on our last day before we were flying out, and got stuck in a storm. There is the T-Rex restaurant and RainForest Cafe if your DS would be into one of those for a meal, which would provide some things to look at, and the
Lego store next to T-Rex. (T-Rex and Lego store are fairly close to where bus drops you off, just pass all the high end stores, so a better choice if it is raining - just would want to call ahead or make an ADR on your app to make sure you could get in to eat). T-Rex has a Build-A-Bear Dinosaur set-up inside. Also there is a bowling alley with a restaurant(Splitsville) and movie theater on the West Side area - probably not what you had in mind at Disney, but just some other options! If it's not torrential, you could also consider taking the bus to MK, and riding the monorail, stopping at each resort to explore( a little more of a pain now probably w/going through security multiple times, but ok if you are not in a rush!), and maybe grabbing something to eat over there - I know a lot of kids love riding the monorail anyway!
You could always try the animation class if you think DS might sit through it and enjoy just having fun trying to draw something, and then eat at the food court. You could also make up a fun scavenger hunt around the lobby/gift shop/food court to spot different characters since there are so many illustrations on the walls(don't know if you have been before) and end in the gift shop or food court, and let him pick out a small item or dessert.
