Dark usually means poor ventilation, which could be deadly, so I would go with those plastic dog crates with the splits for good air movement. I'm just guessing what would be best as I've never done it before.
I would use a large dog kennel and just keep them in there. Feed and water them using the attached dog bowl that comes with them. I wouldn't risk open the door too much or letting them out. I would leave them in the car with your car windows cracked at night. As long as the can stand up and move...