Kennel him for the night or have someone stop by the let him in and out.
60 - 70 will not be 60 - 70 in the car, it will get much hotter, especially if the shade shifts and he's in sun. Crating is a terrible idea as well. People may poke their fingers at him to try to pet or bother him. And you didn't mention it, but camping out - don't leave him in the tent either, They can get wicked hot during the day, even in the shade.