I would suggest anyone new to Crohn's to lobby their doctor to prescribe LDN (see the Low Dose Naltrexone thread for the two latest studies to print and inform your doctor) as it is the least likely to cause serious side effects and the most likely to maintain (or even reverse) the current progression of the disease, in my opinion. It also will not interfere with any other meds--other than pain meds. In my opinion LDN is unique since it seeks to balance and not suppress the immune system.
I am very biased toward a dietary approach to treating crohn's. Good probiotics and omega 3s are a must and make my cramping/diarrhea almost nonexistent. See my post under the Success Stories thread under the Your Story section called MY Supps for MY Dis-ease. This is probably a harder road to take at such a tumultuous age. Cutting out all caffeine, sugars (all real and fake sweeteners: sugar, HFCS, aspartame, acesulfame potassium etc.), smoking, preservatives, unrefined grains and opting for real foods only takes time for your taste buds to transition to. For me, quitting drinking soft drinks was the hardest dietary change. Encourage him to record a food diary for a couple weeks, paying attention to trigger foods--oftentimes crohnnies have sensitivities to dairy or wheat, for example. Try excluding one food at a time and note the results. Surf around this site for dietary triggers or vitamin deficiencies. In the northern hemisphere, people should be supplementing vitamin D3 (2000-5000iu)--especially in the winter.
I had a very nihilistic outlook at that age and I'm sure no one my age would've even wanted to hear about my health concerns--even if I wanted to talk about it. It's a very superficial, ego-based age. Anyhow, Crohn's is not a death sentence and there are much worse diseases out there. That being said, in its own way it is a very psychologically challenging disease since it is not visible to others. It's not visible or certain to yourself either, just how extensive the subtle, unconscious nature of Crohn's is. Only endoscopies, colonoscopies and pill cameras(best for small bowel monitoring) really let one know visibly how good/bad it is. Low B12 can cause emotional effects all by itself and everyone who needs injections often report feeling dramatically energized afterward.
I would encourage your son to find some kind of emotional/artistic outlet. Learn an instrument, play a sport, write poetry/diary or just get frustrations on paper, not to judge, but just get on paper, if only to throw away.
You should be applauded for going this far for your son. This site is invaluable in terms of second opinions and first hand accounts. The first step for you and your son is wanting to know more. Hope this helps.