Hey Dave,
I dislike big to-dos about my birthday. I will be 40 in a couple of months but you know what? I don't even care. I have all I need in my family. I went through a divorce ten years ago. I never would have thought that I would be where I am today. Things can change, brother. Sometimes you have to go out and change them but it's possible.
While I wasn't adopted, I can understand your folks wanting to be a part of "your" day. They love you and want to show you.
Hang in there. Look at what you have and not what ou don't have. Not necessarily material possesions, either.
EDIT: I forgot, Happy Birthday, Dave.