Be sure to stop at the Town Hall, just to the left as you enter the Magic Kingdom and they will give you a birthday badge/pin. My DD age 12 had her b-day last April, we were just lucky enough to have our spring break fall on her b-day. We then had breakfast with Pooh and Gang at Crystal Palace. Tigger did a birthday dance for her, something she and her parents will never forget.
During the day cast members will notice the pin and wish happy birthday. Made one great day. The train conductor was so funny, he asked my dd if we were her brother and sister as we could not be old enough to have a 12 year old. LOL