We've been in WDW for my son's birthday since he was 3 years old. This year for the first time, our schedule didn't allow us to be there on his birthday, we have to leave a few days before. He will be 15 and yes, we will celebrate at WDW for his birthday. I too, as others have said, caution you to not expect anything. All the CMS have always known it is my son's birthday and have never done anything. Anything we do we pay for. Even for our 25th Anniversary, nothing. (This was the only time I was truly disappointed). Many people have said that Disney went far and beyond for people celebrating an occasion, but as lots of CMS have told us, "Everyone is celebrating something all the time". If something happens, it's awesome and magical, but if you REALLY want to make an occasion special, be sure to plan and do something yourself to make sure.
Have a Wonderful Trip!!!