Sports nutrition is basic nutrition- but fine-tuned. Like David Berkoff said, his weight goals will depend on his current position and size. If your son wants to be a 240 lb lineman, he will have to eat like a 240 lb lineman. It's good that your son stays hydrated- some other things for him to focus on are energy-dense foods to ensure adequate energy intake and electrolytes to help delay the onset of muscle cramps.
According to the
American Dietetic Association's position statement on Sports Nutrition and Athletic Performance stated that for athletes; 1.2-1.7g protein/kg bodyweight, 6-10g carbohydrate/kg bodyweight, and for fats, the Dietary Guidelines of 20-35% of the total energy intake should come from fat. So if you take these calculations for his goal weight, you'll be able to determine goal macronutrient intake needs.
One really important thing to keep in mind during any sort of weight gain and sports performance is stomach discomfort. Do not introduce any new foods prior to performance- doing this can result in stomach discomfort. He should stick to foods he knows that sit well with his stomach before a game/practice.
I myself wrestled at a division-1 college and am currently pursuing a career in sports nutrition after becoming a RD. Right now I am in my last year of college, majoring in nutrition.
Good luck!