[/GALLERY]i am local and have had 5 wrist surgeries (2 with extended above the elbow immobilization in a cast) and went to the parks frequently after. Some hints...take it slow. Surgery takes a lot out of you and it takes a while to get your full energy back. Also, As mentioned above, if he's still on pain meds he might want to avoid some rides due to potential nausea. And just in case maybe you should see if your doc can give him some anti emetics just in case....I threw up so much in the parks before my doctor finally gave me zofran. (If he does have to puke be aware trash cans aren't a viable option with side openings, and a trick I learned was to put a seat cover down inside the toilet before actually throwing up, if you can manage....it prevents splashing...yeah, fun times...).
As for crowds, if they are heave be aware that he will get bumped and it probably will hurt. People don't pay attention and honestly most don't care, and even with a cast it can still hurt. Have the rest of your group shield him, especially during and after night entertainment when the crowds are the worst.
Let me know if you have any other questions....I toured the parks a bit differently since I was a local but I can answer any questions you might have! Oh, since you said he will be in a cast it might be fun to know that you can use acrylic paint on them for a fun design! I attached a pic of my first three...the others I did were Darth Vader, Baymax, Jack and Sally and the Queen's heart box... You can really have a lot of fun with them!