He is an outdoors kid, we
mountain bike -- Nope
hike -- Nope
tubing -- Nope
kayak -- Wait a minute here.... look down the page.
But, we don't want him to be bored sitting in the camper/campsite.
He will be, but he will at least be out of the house and he will value that fact.
Get him a decent pair of binoculars or a spotting scope so he can sit at the table and use it to watch nature. If you are at a real campsite and not an RV resort, that may keep him amused for hours.
Now, about the Kayak..
First and Foremost - Get him a good and comfortable lifejacket (PFD). If he has a cast and ends up in the water no mater how good a swimmer he is, he will be in big trouble.
Next, plan to launch from shore, that way the kayak is floating and with the help of at least one other, he can get in (I used to say "put it on"). Make sure he has a flashlight tied to the boat. you won't see him again until dusk.
As a youngun I was also disabled for a time. I went cabin crazy. Any chance to get out even if I could not move from where is was placed was very welcome.
Matt