We have done a birthday illuminations cruise for a family birthday. They put balloons, streamers and such on the pontoon boat and serve a birthday cake while watching Illuminations. It was a lot of fun. My DD loved it when the other boats sang "Happy Birthday" to her and then people on the shore after Illuminations sange "Happy Birthday" to her, also.
We have let our resort know about birthdays and they have sent balloons with a card to our room while we were out. I have read that sometimes nothing happens, but we have been lucky.
Let the restaraunt know it is a birthday celebration with the reservation and when you check in. The birthday person will get a cupcake and an announcement about that special person's birthday. We had DS's birthday dinner at Teppanayki last year, and they brought out an entire cake out for our table. Everyone on the room sang "Happy Birthday" to him.
Get a Happy Birthday button from Guest Relations to wear for the day. It says "It's my birthday".
Have a great time.