for those "almost ready to have a go" you can explain that they can chicken out at any time before the actual take off.
Sit in the aircraft whilst it is parked, if OK
do briefing, fasten seat belts etc, if OK
start engine, stay parked, don headsets and set for comfortable comms, if OK
taxi out, do checks, if OK
line up and roll, if OK
at any point up to the runway decision point you can change your mind and we can abort without actually going flying. Of course, once the wheels leave the ground you are committed to a 3 min circuit.
It worked for my Mum.
Rans6....