for my mom on a wdw bday trip, we bought her a personalized tshirt from disneystore.com now disneydirect.com, we had the disney princesses & "its my birthday" printed on it. she still wears it.
or maybe book a wdw tour or dinner, you can order a birthday cake at most signature wdw restaurants too. i ordered a chocolate cake for my fiance's bday at le cellier steakhouse, it was very good & he was surprised.