Cross Hatch Stitch

I've always had a vague plan to take a long length of French knitting, thread a wire through it, and spell out words or names with it in cursive.
You could also get them into standard knitting, and they could knit squares for pillows, with a French knitting hem. Alternately, you could buy ready-made pillows and embroider the cording on the face (it would be perfect for a Celtic knot design).
Also, they could try using different materials- torn up t-shirts, ribbon, etc. for variety.