Welcome to the forum Kaitlynn, I'm so sorry to hear about your nephew!
You may also want to look into Enteral Nutrition. It's a nutritional formula that is sometimes used to induce remission but can also help with nutrition. You are probably familiar with Boost and Ensure, these are a type of these formulas. There are others which are specially formulated to be easier to digest and more easily absorbed. When you have inflammation in your small intestine, malabsorption can be a problem. These other formulas are easier to digest, so more of the nutrients will be absorbed. A common one used by kids here is Peptamin. Many of the kids here drink these shakes as a supplement to their diets.
My son used it exclusively (meaning, no food, formula only for six weeks) to induce remission and then used it as a maintenance treatment (1/2 dose with regular diet added back) for almost two years. Unfortunately, it's not as successful at maintaining remission and he's had to add remicade. However, he still continues with 1 to 2 shakes a day.
Mineral deficiencies may be contributing to his fatigue. My son was also quite athletic when he was diagnosed and I truly believe the nutrition he gained from these shakes kept him in remission and continue to contribute to his wellbeing.
Its well worth asking the GI about enteral nutrition (EN). Also, it may be covered by insurance... I'm not in the U.S., so not very familiar with your med system, but other here may have advice for you, if necessary.
Here is a link with some info on EN -
http://www.crohnsforum.com/showthread.php?t=36345
As far as crohns itself, as was mentioned above - it's different for everyone! :ymad: Makes it very hard to get clearcut answers! A diary of how he feels, what he's eaten, etc. may help you find some trends/triggers. Also, as Jacqui mentioned, as time passes, you and your nephew will learn how he presents with a flare opposed to a virus (but, even after time, it's sometimes hard to tell). There are no consistent set of symptoms - some people have diarrhea, others constipation, some both, some have fevers, some joint pains, some fatigue, etc.
It's up for debate whether diet plays a role... Most GIs will say no. I don't believe diet will trigger a flare, however, I do believe diet plays a role in controlling symptoms, ie high fibre is tough to digest and can irritate an inflamed intestinal tract, same with seeds, nuts and popcorn. Some find spicy food, dairy or gluten to be a problem. There are members who find that controlling their diets do help, however. Here are links for diet subforums you may want to look through.
http://www.crohnsforum.com/forumdisplay.php?f=268
http://www.crohnsforum.com/forumdisplay.php?f=17
There are a number of treatment options - look through the Treatment subforums for some info. At the top of each of the medication subforums, you'll find a 'sticky' - a thread with general information on the medication.
http://www.crohnsforum.com/forumdisplay.php?f=16
And, feel free to ask any questions!! There are lots of wonderful members and parents here who can help you learn about crohns and all that comes with it! :ghug: