What am I going to tell them?
Keep it simple, go over the basics. Assume that the listeners know nothing.
Some ideas for pertinent points: the differences between omni, cardioid, hyper-cardioid mics.
A practical demonstration of feedback and how to control it.
Mention the 3 to one rule for ambient micing (choir mic) and when it is sometimes OK to violate it.
The importance of having mostly the same vocal mics to make mixing the praise teem / back up vocals easier.
Receiver placement of wireless mics.
Audience participation in problem they have encountered and solution they have come up with.
Hands on mixing experience expressly for those who have never done it.
The importance of cooperation from the band in keeping the total volume controllable.
The use of drum shields.
The proper way to turn on/off the system (amps on last, off first).
You could probably fill a good hour with just basic info. The great benefit the non-techs would gain a greater understanding of what is involved and come to realize it not necessarily magic easy to accomplish.