Given that your son swims competitively, he will have his own unique needs with regard to nutrition. It may be beneficial for you to consider taking him to a Registered Dietician. That professional can design a program specifically for him with regard to his size, age, goals, likes, and caloric/energy needs for swimming.
For many of us on this board who are personal trainers, giving specific nutrition information is out of our scope of practice. But, we can guide you to resources, so I hope this helps.