Tom & Chris Kastle have a great video for kids - the kids at my school just love it. It doesn't deal with the history of folk music,per se, but it presents sea chanteys (often with movements, hand motions,etc.) and also tells a little bit about the origins of that type of music. It's available through their website at http://www.schoonerman.com/sextant.htm Good luck in your teaching endeavors!