Looked it up last night and seems to be safe but some warnings. Definitely no Creatine. It seems to fool around with the hormones which in teens are already whak. It does say protein bars do the same. I did see one warning which said too much protein in a growing body can cause some trouble with kidneys. Will ask Dr. today. If it were me, I would prefer to just eat a protein bar. My sons friend said the drink mix is expensive and I see the bars for $1 in the groc. store all the time.
I've been drinking that stuff for years with no effect other than it helps keep the weight on.
The thing you have to remember is to eat more calories than you use up.
The idea that eating a million grams of protein helps you get bigger doesn't work. What really happens is when you work out properly and drink or eat lots of protein your muscles get stronger and (here is the catch)
MAYget bigger, depending on your body makeup and physique, there is no guarantee. Try protein with branched chain amino acids, it seems to work the best, but bring your check book. Take your calculator and help your son figure out how much he should drink, that way you can keep an eye on him.
Protein is pretty harmless as far as I know, definitely stay away from the exotic (Creatine) mixtures and any type of steroids. If you drink too much protein it will just be an expensive trip to the bathroom every time.
Moderation is the key, like anything else, if you over do it it may cause your kidneys to work overtime. Talk to your son's doctor and his coach.