It's completely normal to worry--I'm much older than your son and have been on Remicade for over two years, and my parents still worry about
Remicade long-term effects.
I think the people who have developed cancer on Remicade were on 6MP at the same time, or previously had cancer to starting Remicade and it reappeared. In my experience, GIs will always recommend Remicade first and surgeons will recommend surgery over Remicade.
My reasoning is to try everything I can before surgery, that way if the surgery isn't completely successful, I can't regret the decision thinking that I should have tried this or that beforehand. Of course, this is tougher for you since you are making a decision for your child...and ultimately, it is your decision.
Does Chris know about/understand the infusion? Give him a hug for me, okay?