The Jepp PPL manual has a pretty good section on the different careers and sectors of aviation. As far as video clips, you could always check your public library system for videos on different careers. They might have something on aviation.
Are you giving a presentation at an elementary school career day?
We had career day for my class of 4th graders a couple of weeks ago. One of my buddies came in and did a great job. He brought in his flight bag and set up a mini cockpit (I made him say flight deck for all of the kiddies.) He had a volunteer come up and did a captain/FO role play scenario. He even tape recorded what ATC would be saying from getting ATIS, clearance, taxi, TO, and finally contacting departure. He had the volunteer FO try to read back to clearances, it was pretty funny. He brought in jelly beans and once we had reached cruise he had two kids as flight attendants to pass them out. Before all this he gave a basic deal on what it took to get where he is and the basic parts of an airplane/how it flies, but a very simple and dumbed down version. If all else fails and the class isn't paying attention, you can always find children's books on pilots.