Genghis
I think the important thing here is that you show the group or prospective group member how you want him to operate your aeroplane. Bit like a company SOP.
Once they are fully conversant with your required method of operation you do a check ride. They are PIC and you simply observe and decide.
It is vitally important that the checkee is briefed on his role as already stated.
No need to be a CRI or anything else. Your aeroplane your decision.