Having recently driven from Ohio To Toronto with my two cats (and having spent over an hour and a half in customs and immigration!), I feel your pain

It sounds like your cats are habituated to car trips, albeit somewhat shorter ones. That's good. My cates *hate* getting in the car, even for ten minutes. And boy do they let me know it. I was pretty worried about the drive since I would be alone in the car and hence would have no one to calm the cats. My vet assured me that they would end up sleeping most of the way. This did not really occur. They did, however, calm down after about an hour or so....

Driving down to Ohio from Toronto, some three years ago, I had tried sedating one of my cats. I don't recommend this. It took hours and hours to kick in, and then my cat was so distressed that I was freaking out. He was falling over, third eyelid rolling over, drooling -- the works.

My vet warned me that the real worry is dehydration. She recommended mixing some Gerber's chicken flavour baby food with water, and giving that to the cats when they arrived. I can't say that either seemed in the least bit interested, but she swore up and down that her cats lapped it up, and were thereby hydrated. So it is worth a shot.

In the end, though, everyone survived. It wasn't fun, but no one was scarred for life. Courage!