I am not an expert on diet for children. I may have a few recommendations from the angle of effects of food on mind:
- No refined sugar, no refined flour
- Rock salt
- Low carb, low empty calories
- High nutrients like vitamins, minerals, and fatty acids
- Very good levels of calcium, iron, antioxidants
I keep finely chopped vegetables in zip-lock bags in the freezer and use them to make whole wheat pasta, ww pizza, uttapam etc. I also keep a homemade powder of nuts+seeds and add it to dough and batter while cooking.
(I am not a pediatric dietician. These recommendations are personal)