I am so sorry to hear that his Senior season had to end early, and under such circumstances.
As
@lanejudy said, you may find it difficult to rent an
ECV for him, unless he has his 18th birthday prior to leaving for the trip. If I were in your shoes, I might consider getting on the phone and calling several of the Orlando vendors that rent ECVs to see if they will make an exception for him. In the spirit of complete transparency however, history has shown us here that the exception is rarely granted.
Regarding walking... remember that the *average* Guest at WDW covers between 5 and 10 miles per day. Even though your son is young, healthy and in great shape as an athlete, he most likely will not be able to walk anywhere near that far post-surgery. Given that the surgeon has already recommended an ECV or a wheelchair, that tells me that the surgeon is realistic enough to know that your son will need some type of accommodation.
If you decide to rent a wheelchair, plan on having members of your group push him - no matter how well conditioned an athlete is, self-propelling a wheelchair at WDW for 5 to 10 miles a day will prove to be nearly impossible... and if he does manage to make it through the first day, be prepared with lots of Tylenol and heat packs for the second day; his arms *will* be very sore. You don't realize until you are on wheels at WDW just how many slopes, hills, ramps, and inclines there are all over WDW. Going down is fairly easy - as long as you can stop yourself. It's the going up (and up, and up, and up) that will get you every time.
Regardless of if he self-propels, or someone pushes him, I always recommend you bring along an inexpensive pair of bike gloves (or golf gloves) to help protect hands. If someone pushes him, and the chair has the old style, hard black plastic handles that are slippery and get hot in the summer sun, the pusher *will* have blisters before the end of the day.
There are other options available; he could use crutches (it makes me hurt just to think about that), a walker (and he could make the tennis balls look like Mike from Monsters Inc! LOL) or a rollator - but those options really aren't realistic for a 17 year old guy. A cane might work (and a folding cane is very handy, and could be carried in a backpack or someone's purse till he needs it) but I worry that it won't be enough help for him, although it might get him further than walking unassisted.
You have the option of letting him try, and then either renting a wheelchair in the park, or calling a local rental vendor to bring one out. Remember that he will still have stand in line for Resort and/or Parks buses, Disney Springs is huge now, with the newly expanded areas, and some of the Resorts can be quite a hike just to get to and from food service, so you may want to consider renting from a local vendor so that he can have the wheelchair wherever he needs it. The biggest concern I would have with the "let him try it" scenario is that I know you don't want him to set back his healing process, and it's so easy to just keep "pushing past" at WDW.
Last, but not least is this: If you are planning on Park hopping, remember that for an extra charge, you can now hop on the Express buses that take you directly from one park to another, always via a Backstage loading/unloading area. Because you have been Security screened at your first Park of the day, you don't have to go all the way back out to the bus loops, wait for a bus, and then go through security again; you are escorted by Cast Members to the bus in a secure Backstage location, and it will drop you off Backstage at the next Park you want to go.
Good luck - and I hope you all have a lovely trip!
