I have been very impressed by the reaction of mothers to Missy Chase Lapine - The Sneaky Chef's approach, and how well it works. As a general principle, adding vegetable puree to everything from pasta sauce to cupcakes is a brilliant first step if you struggle with feeding your kids healthy food. She suggests adding vegetable puree, and applesauce even, to store-bought cake mixes, and oat bran or wheat germ for extra fiber. I can only endorse her idea -- go to her website and check out her latest book. Adding black bean puree to brownies was the first recipe that turned me on to the Baking With Agave book.