Jamie,
I'm sure your family is going to have a wonderful time at the Art of Animation resort. We stayed there recently for my husband's birthday. Even though he is several times 7, he got a real kick out of the Cars theme in our suite.
There are 10 buildings with guest rooms in the resort complex, with Animation Hall and The Big Blue Pool in the middle. You can find a
map of the resort and other information on the main
Art of Animation website.
My husband and I were in Building 2, at one end of the complex. Our walk to Animation Hall took only a couple of minutes -- unless we got distracted by Lightning McQueen, Sally or Flo along the way. So you shouldn't be more than a 5-minute walk from each other, no matter where your rooms are.
Make sure you note on each room reservation that you are traveling as a family group. If you haven't done so, you can make the notation when you check in online in advance. Or you can call 407-939-7429 to modify your reservation.
They always do their best to get your rooms as close as possible.
One of the things we appreciate about staying on Disney property is that you don't need your car, even if you drove to the resort. The free Disney buses run about every 20 minutes to each of the four theme parks, the water parks and Downtown Disney.
At Art of Animation, the bus stops are in front of Animation Hall.
I hope your granddaughter has a magical birthday. Enjoy your time with your family!