It all depends on how much celebrating you want to do , there are character meals (tell the CM when you book) , behind the scenes tours of the parks- like keys to the kingdom .Do remember to get a birthday button from city hall and you will have CMs talking to you all day wishing you a happy birthday etc. If you stop on site let the resevations or guest services desk at the hotel know about the person's special day you may be surprised with a signed photo of a favourite character or plush figure and a birthday card possibly even a cake at one of your restaurant reservartions. All sorts if you just tell the CMs they are sure to help!!
I think you can get flowers delivered to the hotel room (at a reasonable price) using Disney's own florists service too
