There's a recently published book about this very topic, co-authored by two local restauranteurs and a social media consultant. It's a fun read with great case studies and areas for notes/idea workshopping. www.twitterworks.tv
Perhaps they'd be good guest speakers for this Meetup, or at least use the book as a launching point. These guys have certainly figured out where the opportunities lie, how to strategize and execute, etc. I don't know if they're available, but they've got good content if they are!