I got the same letter a few years ago. I thought it sounded fun, so I decided to go and find out more about it. I am very happy that I went! I have been doing the pageant 3 years now and have enjoyed myself each time. I have a friend that WON a couple of years ago, so I know they are legit. They do not try to make you feel forced into doing it, they just give you the information and then they interview you. The Open Call is FREE to attend, so I think you should go and find out about it for yourself. Especially since you are a lot like me, and think it sounds like a lot of fun...because it has been for me!
personal experience, 3 years in NAM pageant