Hi Clara,
I like to make homemade granola, its fantastic with oats, coconut, maple syrup, a tiny bit of brown sugar. Mix with a little sunflower, you bake this in the oven until golden then add raisins. You can serve with milk or yoghurt and berries, and it keeps for ages. Grilled cheese on wholemeal toast is a good alternative breakfast idea and is high in protein, you could also try it with half an English muffin and melted cheese on top and add ham or sliced tomato to add a bit of variety. Smoothies make a good summer alternative breakfast option as you can use yoghurt with them which is a good source of dairy, and by using lots of different berries, you are giving him a great start to the day. A good combination is strawberry, raspberry and raspberry yoghurt.