DS, 7, has a similar breakfast (also allergic to egg)
I ensure that both at lunch and at tea he has a portion of protein, 2-3 fruits/vegetables, and a big portion of carbohidrate (pasta, potatoes, bread, rice, etc)
He gets fruit or fresh vegetables snack just after comming back from school.
He often asks for a bed time snack, which is normally a sandwich, cereal or toast with butter.
All his portions are adult size, he eats far more than I do, yet... he is as thin as a stick.
Now, he can't stay still / stop moving, even when he is sitting he is moving ALL the time. If I am cooking sometimes I find him running in circles around the table 