Of course bdays are special!! Make sure you get a bday button and if you're there ON the actual bday make sure you get a fun card for some extra spending cash. There are limits on it but you can use it at most of the shops in DL & DCA and at World of Disney in DTD.
I second the suggestion for the Birthday Button! You forget you're wearing it- and its so fun to be reminded by Cast Members wishing you a happy birthday!