Just picked this recipe up when I was in Iceland from a cookbook called Cool Dishes. I think kids might really like this recipe, and it's relatively healthy too! A dessert soup might tickle their fancy. The book recommends serving this with crumbled rusks.
Mix the cocoa powder, sugar, and cinnamon in a saucepan.
Add the water gradually, and stir until smooth.
Bring to boil and simmer for 5 minutes.
Add the milk, reheat to boiling point, and simmer for 2-3 minutes.
Mix the potato starch or cornstarch with a little cold water, stir into soup, and remove from heat.
Salt to taste and serve.