Sounds like a fun idea! My group last year did a sword demonstation and panel. We were on the main stage Sunday afternoon. The Twilight Knights Renaissance Guild. I was the dude with the big two-handed longsword. Good times. Make sure that the Con organizers know your interest, and negotiate with them. We'll be doing the demonstration and panel again this year, plus we're in negotiations to hold all-night (midnight to 6 am) boffer battles in the main ballroom every night. Should be tons of fun. We're also negotiating to do katana and knife-fighting workshops. I wanted to also do sword-and-shield, or longsword lessons, but evidently everybody wants to be a frickin' ninja or something.