For the most nutrition for the fewest calories, pick the whole grains made with little or no fat or sugar, e.g. oatmeal instead of Honey Roasted Oats, whole wheat bagel instead of a muffin. Next up on the pyramid are fruits and vegetables. They share the same tier although they aren't grouped together. Get 3 to 5 servings of vegetables, and 2 to 4 of fruits. Both provide fairly similar nutrition so if you or your child can't swallow one, add a few extra servings from the other.
Vegetables provide vitamin A, vitamin C, folate, some calcium and some iron, plus potassium.
Fruits provide lots of vitamin A and vitamin C, some B vitamins, and potassium. Both are naturally low in calories and high in fiber. Go for the fresh version whenever possible. It will have the most nutrition. Choose whole fruit over the juice for more fiber.