I have to give talks like this quite a bit. Like Stringman says, visual aides are great and can potentially drive the whole presentation. A demo of a quick made hatchet bow sounds like a really good idea and fits the group. And like Patrick said, maybe practice by doing a run through in front of a mirror and time it. That way you will know if you have enough material to cover a couple hours of talking. Tell stories about hunting with bows, what bow types work best in different situations, maybe hit on arrow making briefly, if they are preppers go into the best string making material that may be available for them, talk about times you have had bows fail and how you resolved the problem. Sorry, just kinda brain storming here.
Good luck with the talk!
Neal