Many of us find pen hold difficult to teach. We twist their little fingers but they go back to their old positions once we move away. Try a story so they'll remember for themselves.
The Driver has to be comfortable so he has the main seat and waves to other cars.
The Thumb is the Driver's helper. He helps guide the car and does friendly things like warning when a child is running.
The Back-seat Driver is naughty - he keeps wanting to drive the car, BUT you must put him back in the back seat.
If you hold your pencil too close to the tip, you're in the engine! If it's too far back you're in the boot!
The Driver sits in the front seat.