Not sure where you are staying, but we stayed at PP when we celebrated 5 year olds bday last year. They had a package at the front desk for him with stickers and coloring stuff, and a bday button with his name and they gave him a bunch of balloons when we checked in. After that the magic went on and on. All the CM's made a fuss and said Happy Bday. He got to ride Splash Mountain twice in a row, and also Thunder Mountain. Each place we ate at brought him a special bday desert. At StoryTeller's character breakfast, they all came over and sang happy bday to him. When we went on Winnie the Pooh ride, the CM did not notice his button, so son sort of cleared his throat and pointed to his button. The CM quickly said Happy Bday and then when we got off of the ride, he had a personalized bday card for my son from Winnie the Pooh. I'm sure I am not remembering everything, but it was really fun.
I think the special cakes that you can order are really beautiful and I would do that in a heartbeat next time. Also, for a smaller cake, the bday buckets look cute too. I know my 5 year old would have liked it.
Have a great celebration.
Oh, almost forgot, if you go to City Hall, they will tell you that there is a special call for the bday person, and when you pick up the phone, someone special wishes you a happy bday. (I did not do this, but just read about it)