I don't typically drive to my tours, but when kayaking, backpacking and other pursuits leaving a car for two nights never gave me much pause. Parking it on the street in town would be good enough for me. I have left cars longer in park and ride lots as well. Mostly I just don't worry too much about it for that short a time.
That said the few times when I was concerned (due to the longer duration I'd be leaving it), I just asked for permission somewhere or asked the local police what they recommended.