While I appreciate Mike's approach (note to self, visit Mike's coffee table) I find that the attendees at my first few meetings this year have responded extremely well to the educational component, and it seems to have aided their enjoyment of the whiskies. Don't be afraid to be an authority if you feel qualified. No matter what you choose to highlight tell them why it matters and they will listen.
I would make it a tour of house styles. Get bottles of similar age and proof from several different distilleries. Wheat vs. rye is also interesting.