The Polynesian has good childrens activities if you are a guest of the resort. They have a scheduled that is printed in the island times which you get upon check in. They have pool games, arts and crafts in the neverland lounge I think that is like from 12-4 each day but a parents must accompany the child. My 3ds like the arcade challenge. Its from like 3-4 p.m. 2 days a week. You would have to miss the MK parade for that one. They also have hula lessons, torch lighting at 6 p.m.
If you are looking for something for him to do alone, the other poster suggested the pirate cruise and I would also suggest the kids fishing trip. My 3 ds love this. Its like $20 and it leaves from the dock. They did it at the Boardwalk. I cant remember the other pick up places. They also got free drinks. The only thing they did not like was having to wear life vests since they are excellent swimmers, but disney policy for safety reasons. They still talk about it and how the captain used hot dog for bait. This was well worth the money for us. They also have trail rides at Fort Wilderness. Our ds thought this was lame and boring. The horses cannot gallop etc. They are trained to walk comatose like and ever SOOOOOO slowly. But if that interests him, then you might want to consider it. I cant remember the age requirement off hand. You also have the option of having a helmet for safety and reservations are required for both the fishing trip and horseback ride.