Hello, Robin,
Happy early first birthday to your granddaughter! It will be so much fun to celebrate her birthday at Walt Disney World. You'll want to make sure and get a complimentary Happy Birthday button at Guest Relations at City Hall at the Magic Kingdom Park to help others celebrate her birthday, too.
To order a specialty birthday cake, you can work through one of the
three cake delivery options available to guests at Walt Disney World. I think what will probably work the easiest for you is the one where you place the cake order beforehand and have the cake delivered to a restaurant. I'd explain when you order the cake that you'll be picking it up to bring it to the
Fireworks Dessert Party at Tomorrowland Terrace; the closest participating restaurant is
The Plaza Restaurant. Speaking of first celebrations, did you know there is the
Harmony Barber Shop on Main Street, U.S.A. at the Magic Kingdom Park that offers first haircuts? It is an adorable event that might be a fun option if your granddaughter has not had her first haircut yet.
Wishing you a magical trip! Please let us know if you have any further questions. -Kara