Zenkitty, do you have them crate-trained?
Andi, not specifically, but the carriers are often out and open; they don't sleep in them, but they go in and out. Leo doesn't fight the carrier; I open the little door and say, "Get in", and he goes right in and settles down. Percy, who was almost 2 when I got him and was not paid much attention to by his former people, freaks the fuck out when I try to get him in his carrier. He's very nervous. It requires advance planning and a sneaky diversionary tactic to get him in.
Percy's an odd one. He's timid and suspicious; if anyone else is in the house, he'll hide. For six months after I got him, my family was teasing me about my imaginary cat. He's getting better, though. When I went to get him from the people who were giving him away, they warned me a couple times that he was shy and they might not be able to get him out for me to see him. As soon as I walked in their door and said hello, no exaggeration, he came out of the hallway, walked right up to me, and flopped down on my feet to be petted. They were astounded. There was no question at that point that he was coming home with me.
Driving from NJ to VA with Leo was not much of a problem, as much as I'd worried about it. He whined for a while, then went to sleep, and stayed quietly in the carrier the whole nine hours, until we were about thirty miles from our new home (in the middle of the night) and then he decided it was Time to Get Out. When Leo wants out of his carrier? The little whackjob will practically break a tooth trying to chew through the bars. He has a strong sense of personal agency. So I let him out, and prayed he wouldn't get under my feet. I drove slowly and was grateful there wasn't any traffic. He prowled, stared at the world going by, and finally settled down on my left arm. The car being an automatic, I let him, and all was well.