I’ve never come across any legal reason to prevent disabled people being flown. You are in command and if you are happy that the flight is safe, along with all the usual caveats of flight legality like 90-day rule, assorted meteorological minima etc., you are good to go.
Starlight Day at Popham involves flying lots of kids, some of them very disabled. Admittedly these are children and for the most part I can over power them if they suddenly decide to have a go on the controls without asking me first.
Hint: If you get tired of fighting them, there’s always the trimmer….
I took another friend flying. He offered to unscrew his prosthetic leg if it was fouling the rudder pedals. I seem to recall he just took the shoe off the end, which gave a bit more room.
I’m sure your Pax will thoroughly enjoy their flight.