You may want to consult this website: www.drfuhrman.com for some information/inspiration.
Dr. Joel Fuhrman is a physician who advocates a nutrient-dense diet full of the phytochemicals found in fruits, vegetables, legumes, nuts and seeds as a measure to prevent illness.
He explains how, particularly in growing children whose cells are dividing rapidly, the phytochemicals strengthen the immune system and help prevent mutations and future disease.
His approach is very common-sense, not terribly difficult to follow and, IMO, certainly can't hurt (and most likely would help).
He has written a few books, including "Disease-Proof Your Child," which include kid-friendly healthy recipes that are easy to prepare.
That book includes instructions on how to get your kids to eat healthfully.
I feel like I have the most finicky kids on the planet, but they will eat at least some of Dr. Fuhrman's recipes and I'm trying to work more of them into our diet.
Best of luck to you!