I have been on pentassa for 7 years, and have been in complete remission without one symptom from my CD in the colon or ilium. I also follow the SCD diet too. I don't know if it is the pentassa or the diet or the combination of both that is keeping me in remission, but I have not had a fistula or pain or bad BM in 7 going on 8 years, so I am going keep with pentassa and the SCD.
Since your son is newlly diagnosed without a lot damage in his colon and intestines, changing his diet now, might make all the difference for his future. The SCD diet seems to work best at putting people in total remission when it is in a newlly diagnosed person without a lot of previous damage. It is not an easy diet to follow and takes much dedication , but if it works, it is a lot better then taking a lot of hardcore drugs that have a lot of side effects.
I suggest reading the book "breaking the vicious cycle" which goes into detail about the diet and what foods you can eat and can't eat. The way I look at it, you have nothing to loose by trying it, and all ti gain if it works for you.