Simple sewing machine use and maintenance. How to wind a bobbin, oil a machine,what needle to use... and a handout with tips on troubleshooting stitch/tension problems.
Basics of batting, too.
I would emphasize over and over that accuracy when cutting and stitching is what takes the frustration out of piecing blocks and seams.
I would make as many handouts as possible to be used as a reference after the class ...people forget new things easily, especially when there's a ton of info being taught.