Hey Jamie!
Thanks for stopping by the Disney Parks Moms Panel and directing your question to me! How exciting to be celebrating your granddaughter's 5th birthday at "The Most Magical Place on Earth" in September!
You'll definitely want to visit Magic Kingdom Park, which has the most attractions geared for Guests of all ages. Be sure to experience Disney Festival of Fantasy Parade and Happily Ever After, a beautiful nighttime spectacular. Consider booking a magical makeover for your granddaughter at
Bibbidi Bobbidi Boutique followed by a fairytale dining experience at
Cinderella's Royal Table. Your little princess will love being greeted by several Disney princesses while enjoying a meal fit for royalty in Cinderella Castle. The enchanting Be Our Guest Restaurant is another excellent option. Guests may begin booking dining reservations 180 days in advance by going online, calling (407) WDW-DINE or (407) 939-3463 or via My Disney Experience mobile app.
I also recommend Disney's Animal Kingdom Theme Park and Disney's Hollywood Studios for a 5-year-old girl. At Disney's Animal Kingdom Park, don't miss Kilimanjaro Safaris, Festival of the Lion King, Finding Nemo - The Musical and Pandora - The World of Avatar. At Disney's Hollywood Studios, get ready to play big in Toy Story Land, dance and sing at the Disney Junior Dance Party! and be entertained at Fantasmic!, a nighttime spectacular which is a "must do" for my family. Be sure to pick up a birthday celebration button for the birthday girl at Guest Relations inside any theme park.
I hope this is helpful, Jamie! Please reach out again with any new questions. It's my pleasure to assist you in planning a magical birthday trip!
~Jodie