Skip the ice cream, and treat the kids to low-fat frozen yogurt instead -- good for calcium with fewer calories. Add a teaspoon of sprinkles, or layer it with cut-up fruit for a festive parfait.
Next-best choice: Graham-cracker bears. They're relatively low-fat, low-cal cookies made with whole-wheat flour, and they're fun.
Picky-eater idea: Freeze a stick in a kid-size flavored-yogurt cup, and serve it Popsicle-style.