Hi there Claudia, and a warm welcome to you from the Disney Parks Moms Panel!
What a fun time your lucky little girls will have at Disney's Art of Animation Resort! They'll just love exploring all the larger-than-life figures from their favorite Disney movies, and the Big Blue Pool, with its zero-entry shallow areas, is perfect for them to splash the afternoon away.
We've been traveling to Walt Disney World with my son since he was a baby, and we always took advantage of the free pack-n-play available in the rooms. When you check in at the front desk, you can let the Cast Member know you'll need a pack-n-play, and they'll have it delivered to your room. In our experience it may not come right away, so if your little one needs a nap when you arrive, I'd try to stress that you need it as soon as possible. To be honest, it's sometimes taken a couple of calls to housekeeping, but the pack-n-play will show up so your little one can get the rest she needs for all those busy Disney days.
I hope this helps in your planning, Claudia. Please stop back by if we can answer any more of your questions. Wishing you a magical Walt Disney World vacation!
Kathy K.