I also don't understand why the carers sat together and left him alone - even only across an aisle. The width of an aisle can be a long way away in turbulence, with an upset person who needs close support.
That was my first thought. I think you did the right thing F3G.
My airline has a policy of seating WCHR/special needs pax in the window with their carer (if they have one). However this is becoming more and more difficult to enforce quietly and discreetly as more people yell discrimination. (Thread drift) Also finding more people shouting discrimination over not being able to sit in exit row seats if they are nor fully fit, able bodied, etc. I have had a lot of arguments unfortunately about this recently. The PC lot have a lot to answer for.