We were there last year when my son turned 3....we mentioned it to cast members and he got a pin that said it was his birthday....so we attached it to his hat (he had the baseball hat with the ears).....during the parades and passing all cast members and characters, they said happy birthday to him and the characters pointed to the pin. If you're doing a TS meal (especially character ones) mention it and they will sing....we were at Donalds Breakfast (his favorite character) and they all danced around him while everyone sang.