BLT is great for easy access to MK....especially when you need to return to the room for naps, etc. So if you're going to spend most of your time at MK, I'd stay there. Plus monorail access to other resorts for dining, etc and to Epcot. However, if you're going to spend a lot of time at the pool or resort itself, BCV would be better. The pool has a sandy beach around part of it so the kids can dig in the sand or play in the pool, which is really great for young kids like yours. Also plenty to do just walking around....kids will enjoy the boardwalk area.