Hi Kimberly:
This question has many correct answers. I always recommend Animal Kingdom Lodge, especially if you reserve a savanna-view room where your family can watch the animals walk by right outside your window. Upon entering the Animal Kingdom Lodge, your family will be mesmerized by the dramatic lobby expertly themed and filled with African artwork, artifacts, a fireplace (at Jambo House), and huge windows. The pools are great at Animal Kingdom Lodge. Animal Kingdom Lodge Jambo House is home to the 11,000 square foot Uzima pool. The pool boasts a 67-foot slide as well as a tyke-friendly wading pool area. Not far away is a kids playground. Animal Kingdom Lodge Kidani Village is home to the wonderful Samawati Springs pool and kids water playground.
I also recommend Resorts on the monorail. The Polynesian has a relaxing tropical feel, a great pool, proximity to the Parks, and has great restaurants right on sight. I also have a soft-spot for the Contemporary Resort, one of the original Walt Disney World Resorts. I still remember the wonder I felt as a six-year old staying at the Contemporary Resort and watching the monorail run right through the A-frame Tower and marveling at the lobby's 90-foot, floor-to-ceiling ceramic mural created by Disney Legend, Mary Blair. If your three-year old girl likes feeling like a princess, then there's no better Resort than the Grand Floridian Resort and Spa, considered by many to be Disney World's most magnificent, luxurious, and picturesque Resort.
If you are looking at a Value Resort, Pop Century and the new Art of Animation Resort have the best themeing.
Of course, when my boys were 3, all they needed was
a Resort with a playground.