This is an awesome idea! I'm actually considering teaching a course to middle schoolers on etiquette and carriage. Like you, I'm a total manners nut (I'm from the South
) and I scare all of my New England friends with my posture, table manners, proper stationery, etc. Of course, you don't have to go hardcore, but I think it's a GREAT idea. Also great for personal development. I think there are a lot of people who didn't learn this stuff coming up (for whatever reason) but want to learn, and you probably won't just be "preaching to the choir".
Let us know how this turns out!