The other more logical thing to do is just call the doctor’s office and tell them your coming in from out of town and would like to know the post op course to help your son. If not on their website there is nothing stopping them giving you the post op information without his name on it. It’s just sheets of paper. I don’t do knee surgery but have done this type of thing in the past in similar situations.
Also some of my patients would have to go on their “behind” step by step up to their apartment on the third floor. He’s very lucky to have you pay for an Arbnb to help his recovery be easier. He will realize this day 1.