I would not pay $600 more to stay at WL. I have stayed at both and both are great! I think the pool is much better for little ones at AKL because it is zero entry. The adults can enjoy the pool with the little ones, without one of you having to be at the kiddie pool.
I also suggest taking two lightweight strollers over a big double one. There are enough adults to take turns with the kids. Enjoy the AKL's storytelling, restaurants, and animals. WL has its benefits, but not worth the extra $600. The bus service at AKL is excellent. WL has a boat to MK, but it takes awhile because of stopping at FW.