Thank you for the suggestions. That definitely gives me a place to start.
I was a Home Economics (Family Consumer Science-for the younger crowd) teacher for 31 years and retired early 8 yrs ago. I have since been teaching in the local quilt store and through the county park dept with a friend. Although I have spoken to a little larger than class size group, my preference has always been teaching lab classes and small groups.
Becuase of facebook a former student (class of '81) found me and has been quilting because of a project she did in my class. That was the real honor and validation for my years of teaching. It has been wonderful being in touch with her and meeting her quilt friends. This would be for her quilt guild in Toledo, Oh and probably 50-60 at the most. I told her I could do it if I was talking about quilts and quilting.
Several of them had been in my class at the Schoolhouse sessions at the Shipshewana Quiltfest and want me to especially talk about how to make the easy mitered corner with stripes matching. That would be the class in the afternoon, too.
Your answers have been very helpful. Wish me luck.