I make a big pot of quinoa (wash and soak first and cook with a small piece of Kombu seaweed) and make 2 different things that my daughter loves. I recook it with hazelnut milk (but you can use almond or rice too) and then you can add stuff to it: banana, crushed nuts (walnuts are great, almonds, some raisins for iron, pumpkin seed for zinc. You can also freshly grind some flax seeds or better to use hemp seeds as they are chock full of omega 3,6 and 9 and have protein.
For a different kind of taste you can make a delicious broth with miso paste (www.southrivermiso.com has the best miso) and add the quinoa and some fresh veggies too. Add a tiny bit of wakame seaweed for extra balance and nutrients. If your son isn't into the veg, cook them, blend them and stick them in, he'll never know the difference.