When I used to do the courses I would use OHP's for examples of the various primary sources which are easy to photocopy from your home printer and most places have an OHP projector but if you are there to entertain rather than teach then it might be best to concentrate on one persons story.
Look at your research and find someone that you can trace from baptism registers right through the census returns, civil registration and if possible the probate registry. That way you can show how ordinary people like out ancestors all left their permanent mark and we can take snapshots of their lives through the records.
Depending on your time and media available, you can bring in some old maps or photos of locations, what I always think makes a bigger impact on an audience is to depict a female ancestor over time. By showing the life of a daughter, wife mother and grandmother you can get a real insight into the way families were important and how the mother was the solid influence, it sounds cliche but it's true, by focusing on one person it makes people realise that the most ordinary life can be extraordinary when seen as a whole,