I've stayed in both and they are very similar. Based on your sons age I dont think it would matter which one you choose.
Windsor Hills is newer and the majority of homes are large. Both have homes, townhouses and condos available for rent.
The community ammenities are very similar except that the pool at Windsor Hills has a slide in it. It may be bigger as well if I remember WP's correctly....we stayed there back in 2003.
Both have clubhouses with a small fitness center, game room and movie theater. They also have basketball courts, playgrounds, etc. Windsor Hills has a playground area that has a small castle and some other items that may appeal to your son.
Overall I liked both and they are only one street apart so really I think it matters more about the specific home or unit that appeals to you. I would get the best fit for your needs (size, ammenities, price, etc) and not be too concerned with the resort since they are so similar. Have a great trip.