I wanted to know everything when I first started riding. With the assumption that you won't be able to tell them everything a new cyclist would want to know, you might provide them with a list of trustworthy resources on where to get more information. I, personally, turned to TE, Roadbikereview's forums, Sheldon Brown, and Zinn and the Art of Road Bike Maintenance. I also had a handful of of books: Bike for Life: How to Ride to 100 and Bicycle Magazine's New Cyclist Handbook. Certainly, there are a lot more resources out there, but you might give your attendees a starting place to learn more on their own.