Hi Kim,
We love spending time at Downtown Disney. My three boys have always found plenty of things to occupy their time, even when they were quite young.
The first thing that will grab your son's attention may be the train and carousel that he can ride on for a small price. Near the entrance to the Marketplace and across from Once Upon a Toy, there are jumping water sprinklers just begging to be played in. I always bring bathing suits and if the weather is nice, they could spend hours playing there. Luckily there are benches and chairs nearby to sit and relax while they run and play.
Once their fingers have pruned in the water and I drag them out, we like to venture over towards the Lego Store. There are plenty of building areas and legos for the kids to play with. There is also a small toddler play area with a slide. Inside the Once Upon a Toy store you can purchase fun Disney Mr Potato Head accessories or there is a play area to make a potoato or two for display.
Remember to stop in to Goofy's Candy Store for a delicious build your own treat and if you are hungry both T-Rex and Rainforest Cafe are fun places to eat, with plenty to keep your son's attention. If he is into dinosaurs he can Build his own stuffed dinosaur inside the T-Rex shop.
My boys actually enjoyed wandering around the various merchandise stores with me, as there were so many fun things to look at. There are plenty of places to run around and also sit and relax. I think you will have no problem finding plenty of things to keep all of your attention. You can find additional information on everything Downtown Disney has to offer
here.
Wishing you an amazing time!