I'd assume there would be a popup that says in clear terms "Device XYZ was used to view your location" or whatever, and a button you could click that let you see all linked devices and kick them from your account.

IMO cars shouldn't have parental controls. If you had your kid the keys, you're giving them control. It's one of the first seriously adult things kids are trusted to do, and that trust should not be partial.

Whoever holds the keys owns the car. If it's stolen, that can go through a court. Otherwise, remote control should be subservient to whoever is actually in the driver's seat.

You go to the settings in the car screen and remove that device from the list of authorized devices.