eh, I am with MAKG on this one. They got to learn how to do it. I am glad that the kids dad took the time to go out and teach her to how to do this. more learning and more practice will make a better driver, and that isn't bad in my opinion.
If they hit your truck while practicing, that is when you can get concerned. more than likely, they will only tap it and do nothing to it if they do hit it, and If the father is responsible enough to take his kid out to teach driving skills, he will be responsible enough to exchange insurance info with you if the truck does get damaged.
And if you are worried that someone will hit and flee, get full coverage insurance on it and call it good...
AJ