This is a great (and very easy!) project for children of all ages. Older kids can create very complex designs, and younger ones can just scribble and still produce great works of art!
You will need:
Water color paints
Water color brushes
Container for water
Begin by drawing a picture or design with crayon. Dip your brush in water and lightly wet the paper. Then paint over it with watercolors. The paint should be very watery, not too thick. This will create a nice "wash" effect. The paint will fill in everywhere except where the crayon
Some neat ideas:
Use a white crayon for your picture or design. Since it's harder to see white crayon on white paper, try tracing your design/picture lightly with pencil first.
Place a leaf or f under your paper and rub the crayon over the paper to create a plant "rubbing". Then use the watercolor wash.
Lay your paper flat on a textured surface, like the sidewalk, or brick wall. Rub the crayon over the paper for a texture "rubbing". Then use the watercolor wash.