Hey Howdy Hey Kirsten,
Thank you for your question. Celebrating with the Mouse for your daughters birthday is going to be a memorable occasion. It is completely fine to celebrate her birthday on a later date; the Disney Parks are all about making their Guests feel special no matter the occasion!
Be sure to stop by Guest Services at any of the Walt Disney World Theme Parks and tell them you are celebrating your daughters birthday. The Cast Member will give her a free "It's My Birthday" button for her to wear; she will be sure to get birthday wishes and smiles all day.
We always love to have some one-on-one time with Characters; so we reserve a Character Dining Experience. Located at Magic Kingdom, Cinderella's Royal Table, is an excellent place to celebrate a birthday. Disney Princesses will mingle with Guests for photos and autographs while you dine in a Fairy-tale experience.
You can also sprinkle some more pixie dust on her day by ordering a personalized birthday cake if you're dining at select table service restaurants. Call the Disney cake hotline at (407) 827-2253 to order one, they will need at least 72 hours notice prior to your magical date needed.
You can also contact Disney Floral & Gifts. Their Dream Makers can help you plan anything including an in-room birthday celebration for her.
I hope this helps and that you all have a pixie-dusted visit. If you have any more questions, please visit us here at the Disney Parks Moms Panel and let us know how we can help you plan your magical vacation.
Wishing you magic!
~Lynette