You'll love this two-in-one project: a highly original valentine that moonlights as a usable ball of clay.
An older child can make the play clay (with adult supervision) while a younger one makes the tags. Then both children can roll and cut the clay hearts and bag their own valentines.
Mix the flour, salt, and cream of tartar in a medium saucepan.
In a separate bowl, mix the liquids, adding drops of food coloring until you reach your desired shade.
Pour the liquid over the dry ingredients and stir. Cook over medium-low heat, stirring constantly, until the mixture holds together and gets too stiff to stir (it will stiffen even more as it cools), about 5 to 10 minutes. Let it cool.
Knead the clay briefly, then roll or pat it to a 3/4-inch thickness and cut with the cookie cutter.
For each valentine, place a clay heart in a cellophane bag. Cut a tag out of white paper, decorate it with markers, and punch a hole in one end. Thread a length of ribbon through the tag´s hole and tie the bag shut with a bow.