In reply to the original post of using checklists for trial lessons - yes, for the power and vital actions.
If the punters don't like you being professional, tough!
I fly four different types of light a/c each with slight type differences. There is nothing wrong with consulting the checklist whilst doing the vital actions.
As for teaching students on a course, yes they should memorise the checks eventually, but the point of a checklist is that it is there so you DON'T forget something vital.
If they do parrot it then do as Twincomm suggests and pop the fuel gauge fuse. That always wakes them up!
To date I have never had a trial lesson quetion why I use a checklist, after all thats what most of them expect you to do anyway.