Good for you. Ignore PaintMan's stupid comment.
My dad is 86. He is not in a wheelchair, but he sure wouldn't consider climbing on a ladder (or even under a sink) to cut out a bad section of copper pipe and sweat in new section.
Playing with fire in a confined space is not a safe activity for anyone, of any age, with limited mobility.
If a ladder is needed to solder a fitting, it will probably also be needed to cut the pipe and install the sharkbite. If the ladder is the issue, it's best he hire a plumber, or get a friend to do the work. It's not that hard of a job, so any able person can do it.
The age comment is questionable, but the potential for a leak with a glue patch is spot on. I'd either solder or cut it out and use a Sharkbite.
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