That is great. Seeing the age of your kids, they are going to love it--and you will as well. The proximity to Epcot cannot be beat, as well as DHS. The Boardwalk is great. We own at BCV, but are are coming down next week for a quick 5 nighter at BWV. Couldn't get into BCV on short notice, but we're happy to just be in the Epcot area, we find it so convenient to our interests. We are back in November and will be at BCV...and can't wait for that, but am excited to try out different places (we are also spending one night next week at AKV).
Enjoy the vacation, enjoy SAB and all the fun that is to be had in the area. I would suspect you won't have too hard of a time selling him on an add-on after a few days there!