My son and his wife always brought their cats with them in cat cages when they moved around the country. Both kitties were checked out by the vet and received health certificates...as well as sedatives if they were needed...for the kitties, not for son or his wife...
The cats did well....and had small litter boxes in the car to use if needed, along with plastic bags to hold wastes and soiled litter.
Since your cats are older, ask the vet. With the current heat engulfing many parts of the country, I'd be very concerned about the well being of your pets in cargo. Just recently read of pups that died in cargo because of the heat....was okay when loaded, but then there were delays and then the heat increased.
You might also ask if you will need a health certificate for traveling with them. Always had to have one for the dog and my kids have always had one for their cats.