D.,
Have you thought about adding more protein to your son's diet? The analogy I like to use is that of building a fire. When you build a fire, you need paper and wood. The paper burns fast and the wood burns slow. The same is true with our diet. A huge bowl of cereal is like "paper", especially for someone with a fast-burning metabolism. All of the snacks you mentioned (veggies, fruit, crackers, yogurt) are healthy foods, but they might not have the "staying power" your son needs. Some suggestions: nuts, trail mix, hard-boiled eggs, celery and almond butter (or peanut butter if he's not allergic), cheese. It's especially critical to start the day with protein...instead of cereal, consider eggs, a smoothie with protein powder in it, steel cut oats with nuts and fruit. You get the idea. Good luck!!!