We'll be there this year also, but haven't been on a 'regular' birthday before....only the 55th and the 60th. My daughter and mom both share a birthday with
Disneyland. They did not do much 'birthday' stuff on the 55th, so I am not expecting much this year. If I'm remembering correctly, that year they played the opening speech and had some characters along the railing of the Main St train station and then later in the day the schedule said there would be the happy birthday song by the flag pole...but there was a great flash mob and CMs and characters came pouring out of the backstage areas and had all learned a choreographed dance....after the dance we all got to mingle with them and it was lots of fun.
Last year, was similar I think but there were also cupcakes most of the day. I feel like that was about it? I do remember workers lining Main Street and giving hi-5s as we entered in the morning...maybe they do that every day, but we never get there that early HA! I feel like the birthdays are pretty low key. I do know that the crowds have actually been LOWER than I expected each time. A lot of the people that were there were waiting in lines for birthday/limited edition stuff that was only available those days.