An Alexa or Google voice activated assistant (and setting it up for them), so they can watch movies, play music, etc.

3 months of netflix, prime, audiobook membership, etc

Tobii eye-tracker for gaming/mouse movements, foot pedal buttons

Foot dexterity toys, balls, rocks - so they can get better using their feet and toes.

A ebook with voice activation

A big touch screen monitor hooked up to their cellphone / computer so they can do computer stuff with their feet. And screencast/chromecast to a big tv display. So navigate with feet, and big display for easy viewing.

A huge cost-co sized bottle of anti-diarrheal pills.

A stadium pal, or leg strapped urinal device.

Gag gifts

Sign up for you friend to get visited by the mormons or the 7th day adventists (I mean, he has to fill his days doing something, right?)

Cattle scratcher post

fleshlight mounted on a pole

Juggling balls.

Then spend a lot of time hanging out with him while he recovers.

A long-handled scratcher. For reaching places that the casts are now not going to allow his arms to bend towards.

His arms are also going to get itchy AF inside those casts.

And for shits and giggles, get him a few rubber model cockroaches to stuff down inside those casts the day of their removal. Or really, any small rubber insect that is disagreeable to most people.

Rubik’s cube

As someone mentioned, an Alexa speaker. You mentioned a young kid and Amazon Kids has some great audio games you can play. I've had a blast either playing along with my kiddo or just watching him. Plus you can connect them for use as an intercom.

Occasional outings and a change of scenery might be appreciated as time goes on.

If he likes music, a good sound system.

Extra long straws for drinks.

For gaming, I highly recommend a trackball mouse since it requires so little movement, and depending on the model the buttons don't require a lot of force to be pressed.

A quick google shows me that these work even on an xbox.

I would suggest a fingertip trackball, and one with the largest ball diameter you can find. The larger the ball the more accurate and less movement needed.

https://www.amazon.com.au/Kensington-FusionTM-Wireless-Trackball-K72363WW/dp/B08D356XB6/

^ This is my daily driver, but it is better suited to someone with small hands.

https://www.amazon.com.au/KENSINGTON-K72359WW-Kensington-Wireless-Trackball/dp/B00009KH63/

^ This is the easiest to use, most comfortable for almost anyone with larger bands, and requires little force to click.

https://www.amazon.com.au/Kensington-Orbit-Trackball-Scroll-K75327WW/dp/B07YVMXLQC/

^ This is another smaller contender that may be easier on his hand, as it is more rounded. Some people need flat, some need round.

Put a washcloth under the left side of whichever one he chooses so he can adjust the tilt so his wrist won't hurt.

https://www.amazon.com.au/Elgato-Stream-Deck-Pedal-footswitches/dp/B09PRMCTGB/

^ Something like this would be good for the first little while, he can drive with the trackball and use his feet to click. There are lots of these at different price points.

For comfort, things to ease the itch and miserableness of the casts that will come. It keeps you up at night.

https://www.amazon.com.au/CastCooler-Immediate-breathable-orthopaedic-manufacturer/dp/B003XNNCV0/

^ Very cool product I wish was around when I had a cast. Seems well reviewed.

https://www.amazon.com.au/Scratcher-Cleaner-Sanitizer-Cleansing-Included/dp/B092472C4Y/

^ These to scratch itches down the cast. He should put nothing else down the cast, and don't put it so far down that you lose it. The skin under the cast will become very thin and fragile, anything put down it with a sharp edge could scratch and the warm moist environment could breed infection.

Regarding toilet time, if the bidet you got does not have a dryer function he may need to dry his booty when he's done. Many homes that have bidets everyone has their own little towel they use. He could move a stool or something in the bathroom and put a specified towel over it to sit on to dry himself.

My condolences to your friend, really glad he has a friend to help him.

Gimble vice and a fleshlight?

There's a game you control by blinking. Before Your Eyes. It's a fairly short indie game, and maybe a bit heavy, but he should be able to play it just fine.

My friend’s wife just broke her arm, so I sent her this: A Farewell to Arms: The Hemingway Library Edition

https://www.amazon.com/Butt-Scrubber-Body-Wash-Aid/dp/B074YC6V2J