Guest List Concerns

I know that I have been MIA lately...sorry!! I plan to recap our wonderful trip to AZ this weekend...I got some great pictures of the game. I am still in shock that the cardinals are actually going to the superbowl! My fiance is going to make the trip to TB...I am very excited for him! Anyways...

I have been working on the invites. I now have them designed and am going to go have them printed very soon....but before I do that I HAVE to finalize the guest list. This leaves me pondering a few things....

1. I work in an Elementary school...because I am a PE teacher I work and interact with all grade levels. I am unsure how to do the invites. I do not want to offend anyone...but I cannot invite the entire 100 person staff. What is the correct thing to do?? I plan to invite the 10 people/couples that I interact with on a personal level...but I just hate to hurt someones feelings. I thought about putting an invitation in the lounge (it is a 2 hr drive to our ceremony location- so dont really think too many people will come), or is this tacky? Any ideas?

2. Did you ever have people that you didn't plan to invite ask if they can come? What do you do? I have been saying sure and keeping a list...do I go ahead and invite them even if I wasn't going to in the first place? How do you tell someone that they are not invited? I find this too be really akward...it is not like we are throwing a huge-dont-want-to miss-it party??

Any suggestions would be appreciated!!