I've been on Remicade since October and have had mixed results... At the beginning, when the infusions were only a few weeks apart, I noticed significant relief from my symptoms right away. But as the infusions got farther apart, the relief became less and less - my doc is doubling my dose for the next infusion, so we'll see if that helps. My last scope found that the Remicade has been working to reduce my inflammation, which is another plus.
As for what you should expect... Your son's infusion tech will probably give him Benadryl and/or Tylenol to help protect against any allergic reaction before each infusion. At my first infusion, they gave me IV Benadryl and it made me pass out pretty quickly. Since then, they've been giving it to me in pill form, but it still makes me drowsy for the rest of the day. I don't do anything special for the infusion (except take a half-day off of work!) - I just show up, get jabbed, and either watch TV, listen to music or read a magazine while the stuff drips in me.
I'm sure you've heard it before, but I'll say it again - this disease is different for everyone, so there's really no telling how Remicade will affect your son's disease. Here's hoping that he has good results with it!
Best of luck to both of you! Hang in there!