One thing to keep in mind as you contact people to get their cooperation with shooting: they ALWAYS start with NO!
Gaining access to your population can be one of the most difficult parts of any documentary. Most people don't want to be bothered, don't want to be on-camera, don't want you to interrupt their "real" business.
It's up to you to be convincing. To be persistent. To be honest. Seek out compromises....don't stop with that initial "no."
And if nothing else, just show up at the event and ask again and again and again and again. That's how Z-TV was able to get a one-on-one interview with John Kerry in the 2004 election race. One student who just NEVER gave up asking. She wore them down. The no turned to yes. Good docs don't happen easily. It takes persistence and vision.