I guess I'm the resident expert on this subject...
I don't have fingers, so I've had to deal with this since they first brought in the scans. First off: They do NOT scan your finger print, they scan the shape and size of your finger. If you have fingers, whatever is there should work with the scanner. If the nature of your injuries means that the geometry of your finger tips may vary over time, that might be an issue, but it can be managed.
Before they started switching over to the MagicBands, I was able to have them turn off the requirement for the biometric scan on my Annual Pass, so when I put my pass through the turnstile it would open without a finger placed on the oval. During the transition to MB, they wouldn't do that any more. Now, with the new system, I ask for a Guest Relations staff person with the iPad and they scan my MB and I show a photo ID and they let me in. It slows me down slightly entering the park if a GR person is not readily available, but for the most part it's relatively seamless. Once I was asked what park I had visited the day before as an "added security" question, I was totally thrown by the question and had to ask my son [I had a brain-block and couldn't remember], the GR staffer accepted that one of us had the answer...
I haven't tried to get the MB set up to not require the biometric scan since the system has fully switched over, simply because it's not that big a deal to have ID out and ready.
