I am a student, not an instructor, se excuse me for trespassing.
In my dojo, we have 50+ people who practice with good spirits and viguor, and young people who come to pass time and socialize. They are afraid to take Ukemi, and find Nikkyo too painful. This kind of people will be already lying down on the mats before you even start the technique. I think it is not a matter of age or disability. It is a matter of spirit. Either you have it or you don't. Of course, I would rather practice with the first group rather than the second.