Hi Deepa,
How exciting that you are visiting Walt Disney World for the very first time and celebrating not one but two special occasions!
You can absolutely celebrate your daughters 5th birthday during your trip even if it will not be her actual birthday whilst you are visiting.
Be sure to collect some anniversary buttons for yourself and your husband as well as a birthday button for your daughter from guest relations when you enter a Disney park for the first time. You will be able to wear these throughout your trip and will be surprised at just how many Cast Members and other guests will stop to congratulate you or wish your daughter a happy birthday.
Perhaps you could consider making a dining reservation at a character meal to celebrate your daughters birthday? You can find out more about the various character meals available
HERE. These can be booked online or by calling (407) 939-3463 up to 180 days prior to your visit.
You could even arrange to have a birthday cake brought to your table during the meal for her. Specialty celebration cakes are available for an additional charge and should be ordered 48 hours in advance by calling (407) 827-2253.
Wishing you a magical trip!