I hope that this suggestion will be helpful, Mark. I would begin by letting them get familiar with the paints and do somewhat of an abstract. I would demonstrate how to achieve a transparent color, opaque, and blended color. Explain about bleeding of color etc. so they may get the feel of the paint. When complete they could creat a line drawing or landscape over the watercolor. One thing I would do would be to let those who want to work realistically do so, yet I would also allow those who wanted to be a bit more abstract do so as well. Using mask type products on the paper ( rubber cement etc.) or salt for texture is also good because of the "uncontrolled happening" that takes place. I hope that I am of some help. I teach 1-8 and a 7-8 advanced placement class, 500 strudent's in all, and I have always found that the magic of the process is always one way to entice your student's. Look at whether the adult's are there to become artists or to learn and have fun. It would make a difference I guess. D.