Here is a Supreme Court ruling that clarifies it:
The elements of care and control are:
(1) an intentional course of conduct associated with a motor vehicle;
(2) by a person whose ability to drive is impaired, or whose blood alcohol level exceeds the legal limit;
(3) in circumstances that create a
realistic risk of danger to persons or property
In this case, the Supreme Court held that the risk that the car be set in motion must be a
realistic , as opposed to a theoretical, one. If all that was required was a theoretical risk, then anyone found drunk in a car with any access to the keys would be convicted. While the standard was not meant to be a high one, this was clearly too low and would capture innocent or benign conduct.
Be careful where you fall asleep: The Supreme Court reviews the offence of impaired care and control | The Litigator - Kingston, Ontario
The case was one where a Quebec man wakes up one morning after heavy drinking, and has to leave. He calls a cab, gets into his car to wait and turns on the heater (keys in the ignition) to wait for the cab. The cabbie found him asleep at the wheel.
The man was acquitted.
So getting back to the campfire example, if you are drunk and headed towards your car, and the obvious conclusion is you are going to drive drunk, you could be charged. If you were just heading there to get a pack of smokes no problem. (if you can prove that).
As for the opinion on private property, I was witness to an incident where an upstairs neighbour was asleep at the wheel, passed out and the police were called on a noise complaint. The car was in the driveway. My van was behind it, so the car could not move. The police threatened to charge him with impared care and control, but did not. I moved out of there a few weeks later.