We have stayed in both, so here is my honest take on them.
OKW is larger, no sofa, older,decoration is dated and it has more of a hotel room feel. It is a lot of walking or waiting for the bus. We always ask to be near a pool and its about 50/50 us getting that request. We have always felt that it was a good value for the points...just be prepared to do more walking. Not to bad if you have your car with you. Hospitality House has activities for little guys (arts crafts etc..) its just farther from your room.
BWV have the option for a standard view which will save you some points. The rooms have more of an apartment feel as stated above, close to Epcot and MGM. Lots more going on in that area. The boardwalk at night is fun you feel like your on vacation with options for things to do without planning.
I think the pool slide is a bit more fun than at OKW. My nephews really liked the Hospitality House by the quiet pool at this location. It seems to be larger with a bit more for them to do. Its close to most of the rooms and they also have activitys for children.
Have you thought about BCV? I know its really hard to get in if you dont call early but you might try to waitlist and see what happens. This place has the largest sand bottom pool in the world (per 2005 travel guide I just read

) Hands down the best pool in all of WDW if that is important to your son. Of course the danger is that he wont want to go to the parks and will just want to swim???
Bottom line, if I was on a serious point budget, and I just wanted to be at WDW I would go OKW.
If I was just watching my points and had a little bit of flexibilty I would ask to waitlist for a standard view at BWV.

For the convience of being near two parks and lots of activity around the boardwalk.
If I found I had more points to use than I thought, I would also waitlist for BCV for the amazing Pool!
Hope this helps!