I think Bob has done a good job of describing the access to goods in Jarabacoa -- they're all there, but the pricing is different (some things are more, others less). If your son wants to make friends, there's a coterie of shoeshine boys on the plaza there. They range from about 10 - 14, and they seem to be pretty nice. Let me suggest that if you want to be the most popular people in town, you can bring with you a baseball bat and a couple balls. The balls you can find in the DR for a reasonable price, but for some reason bats are beyond the means of virtually every family in the country (us $120 and up!) You can pick up a nice aluminum bat at your Wal-Mart for about $25, or at a yard sale for next to nothing. Trust me when I say the response will be well worth it.
While you're there, be sure to visit Salto Jimenoa One. Because they are easier to access, the guides in town will try to get you to go to the Salto Baiguate and Salto Jimenoa Two, but you should insist. This is the falls from Jurassic Park, and it's spectacular (a tough walk back up, though).