It sounds like a great project. Definitely, start with the basics. Demonstrate brush techniques and methods for developing line, texture, space, color, and shape. Create a color wheel. Demonstrate masking techniques. Use masters such as Winslow Homer as guides. A simple chinese landscape is a good way to start.

You can find an example at
http://www.artmuseums.com/china.htm

There are other very good watercolor links at the following websites:
ArtSonia Lesson Plan-Woven Watercolor
http://www.artsonia.com/teachers/projects/plan.asp?id={5FF2B47C-998A-401F-9639-200A7A221257}

Artsonia Lesson Plan-Upside Down Painting
http://www.artsonia.com/teachers/projects/plan.asp?id={198B9B24-EAEC-446B-8874-8A1203C41231}

Watercolor Demonstrations-Mary Crowley Kiggins
http://www.multimediaarts.com/watercolors/demos.htm