While Grandparents may be old hands at this love business, they're never jaded when it comes to finger-painted cards created by their school-age sweethearts.
Let your artist whip up a batch of finger paintings. (You may want to create a personal workspace with by laying out some newspaper)
Let the paint dry and then cut various heart shapes from the finger paintings.
Glue the hearts onto a plain card, along with ribbon or other finery (save one heart to glue onto the back of the envelope).