I want to say a few things to any of the shy runners lurking here and not saying anything. I am one of you. My fastest time remains 3:05 in the
Disneyland 1/2 although I don't consider that my PR since it contained no stops whatsoever and every race since has contained multiple picture and/or character stops. Don't be intimidated by how fast you aren't. Instead, take advantage of the opportunity to learn from some very fast runners who don't care how fast you aren't.
I can honestly say that my first 1/2 marathon was not a "fun" experience. It was something I had to overcome, endure, and accomplish. But every race since then has truly been fun. And part of that fun came from learning from runners here about how to cope with the mental part of the game and see the bigger picture. Don't let your fear of how fast you aren't hold you back. Because at the end of the day if you're wearing your medal around Disney, nobody cares that you were "slow." I've tried to persuade many who admired the medal that earning it wasn't the impossible task their mind made it out to be.
Difficult, yes? Impossible. Never. Walt Disney said it best: "It's kind of fun to do the impossible."