I helped my Dad move from WA to FL with his cat. In the weeks leading up to the day, he acclimated her to the car. First, just let her explore the car, then turning it on but didn't move it, then he started driving to the park about a mile away. When the time came, she was pretty vocal the first couple hours. But we would talk to her, and we'd pet her. She was very responsive to her name. Our drive took 5 days. On Day 3 she tried to hide in the hotel room, and didn't want to go back in the carrier. On the last day, she was over it. She just curled up and slept, totally ignored us. When all was said and done, she was more freaked out by my parents' temporary 1 bedroom tiny apartment after having a huge two story house to roam around in, than the car ride.
For only one day, I would just work on acclimating the cats to the car in advance. Try to make it a positive thing, reward with treats.
The spray, another poster mentioned is probably Feliway.