Hi Christy, Your vacation will be here before you know it!
Our family loves Saratoga Springs Resort. The main, "High Rock Spring Pool" is wonderful. There are rocks with cascading water around the zero-entry pool. There is a waterslide, two whirlpools and a play area for kids. In addition, the different sections also have their own smaller pools.
My Dad lives in Tampa, and he has come to visit us when we were staying at SSR. We enjoyed a fabulous meal at the Turf Club and relaxed by the pool together. You could even take the boat ride over to Downtown Disney with your sister and nieces.
If you were staying at the Yacht and Beach Club, your sister wouldn't be able to join you because Stormalong Bay (the pool there) is strictly for Y & B Club Resort guests only.
By the way, I answered a question regarding room location at Saratoga Springs that you may find helpful. You can read that:
HERE. Enjoy your vacation and your visit with your family!
Kaylene