This was a hard one, anything I thought of used candy in some way. What kind of healthy are you looking for? Would jello jigglers, or rice krispie treats cut into hearts be too sugary?
Other recipes I came upwith include: Frozen fruit and yogurt pops in pink and red, Nutty jumbles which are made with chopped almonds, pecans and walnuts and chould be molded into heart shapes before baking, and I also have a recipe for apple jiggles which uses apple juice, unflavored gelatin and cut up fruit and can be cut into heart shapes like jigglers. Let me know if you want any of these recipes.
How about baking your child's favorite muffins and putting plastic valentine picks in them?