A friend of mine crashed a week after passing his test (at 17).
I was in the car with a newly passed driver when I was 16, and he aquaplanned round a roundabout in the rain, couldn't control the vehicle. We were ok though.
Another newly passed driver, in their car, was driving too fast (I was 17), tried to race another car for fun, until I screamed at him to slow down...further up we came to an accident. It was the car we had raced. Upside down.
How much control you have over your 17 year old getting in the car, not much. But I would be very worried, and would make my feelings clear.
My kids know about my experiences (been in a car crash, and brother in a serious car crash, school friend died in a crash) they are already saying they wouldn't get in a car with a new driver or bad driver, 17 year old or 47 year old.
Sorry that's no help. I do get your worry though.