How old is your kid? As much as the Poly is my favorite resort, I think with kids I would LOVE to stay at the BC just for the pool (and the character breakfast at Cape May Cafe!)
The BW's pool is pretty awesome, too, but obviously not on the same scale as the BC.
If your kid is older, they might appreciate the Poly (and being able to see the castle while swimming in the pool!) The slide is awesome there, too. Pretty scary and great for bigger kids.
Gee...I didn't help much, did I? I just provided arguments for each of your choices!
Sorry...
I think ALL of your choices are GREAT!