Hi Ekira! Although I was too young to remember my first time to Walt Disney World, I will always cherish the memory of taking my son for his first time. Make sure to pick up a complementary First Visit button from Guest Relations or from the front desk of your Walt Disney World Resort.
I always add the Disney Dining Plan because with all of the planning and budgeting that goes along with a vacation, its relaxing knowing that I've taken care of the food expenses in advance. It's one less thing to worry about while on vacation. The Dining Plan would also present a great opportunity for your daughter to meet her favorite Disney Princesses. Character Dining experiences are always on our "must do" list, and sometimes we plan whole days around them.
I have a son, so I don't get to venture too far from pirates and princes, but I know that if I were twenty years younger I would most definitely try talking my mother into taking me to
Bibbidi Bobbidi Boutique. Here your daughter can be magically transformed into her favorite Disney Princess by her very own Fairy Godmother-in-training! If your daughter loves dressing up and being pampered, this would likely be one of the highlights of her trip. While some of the packages can be pricey, you can save a bit of money if you bring a princess costume from home rather than buying one from the Boutique. Also, since you mentioned that you have 3-day park tickets, I would suggest spending a non-park day at Downtown Disney and visiting the Boutique location there. This way, you can maximize your time in the parks and still get the royal treatment at Bibbidi Bobbidi Boutique.
If you have any more questions please don't hesitate to ask. Have a magical first Walt Disney World vacation!