Trying to teach a bunch of people.

So my local library has been hosting a sort of video game day every month. I asked about a dnd game being added to the activity's, one thing lead to another and now I'm going to be teaching a class on Dungeons and Dragons 4th. Can I get some suggestions on how I should conduct this class. So far we we have 2 classes. the first one will be about the basic rules and I'm going to create some characters and run some people through and teach the rules. the second class will be about character creation. I don't have a lot of resources and 2 weeks to figure out the first class. Please help.