I have had too many foot surgeries which left me non weight-bearing for a month after each surgery. I realize this is nothing like a knee surgery where you cannot bend the knee, so the only comment I will make is that you might want to buy two shower stools: one to sit inside the shower, and one to sit outside the shower.
My five-sided glass shower has a five or six inch lip, so I had to scooch bench over to the shower entry, pivot myself from the bench outside the shower to the bench inside the shower using only the one good foot, and then reversing those steps to exit the shower. It was useful to place a towel down on the bench outside the shower to prevent slipping.
If the Airbnb has a different shower set up, there are also transfer shower benches, where a section of the bench sits outside the shower and another section inside, but that wouldn’t work for me because I needed to close the glass door. I have to say the most dangerous activity.
I am guessing that he would not be allowed to go up and down the stairs on his bottom? I used one of those knee scooters, and parked one at the bottom of the stairs and one at the top of the stairs, and then went up and down the stairs sitting on my bottom.
My son stayed with me this summer for three weeks after his ankle surgery, and went up and down the stairs on crutches. I could not watch.
Best of luck.