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
There are other very good watercolor links at the following websites:
ArtSonia Lesson Plan-Woven Watercolor
Artsonia Lesson Plan-Upside Down Painting
Watercolor Demonstrations-Mary Crowley Kiggins