Some cats are great travelers, others are not. It depends on the cat, but often it is easier if you start them young. I have traveled many times with cats and never used a cage and never had a problem in the car. Unfortunately we lost one cat a gas stop because it bolted when the car door opened and never came back.
My suggestion is to take the cats one at at time, then together on some short local trips. See how they react and judge from there. Some kitty treats and extra attention will help. It will be easier if you have at least 2 humans in the car so the cats can get some attention without distracting the driver. Use the carriers, but consider letting them out one at a time if they travel well. Put them back in the carriers well ahead of the stops. Perhaps you could even have a 3rd carrier for a kitty latrine. They would likely appreciate that courtesy.
No matter how well they travel, secure them well before opening any door (car or hotel). The temptation to run just might hit them at a bad time.
I have fond memories of my trips to and from college (400 miles each way) with my cat "Junior". Thanks for bringing back the memories.
Oh, BTW, some cats stress really bad traveling. If yours freak during the short trips, you vet may have some suggestions.