@chai2,
The older cats won't go in the same carrier...nope nope. Queen Black Cat Magikistan would never have it. Her poor (bigger) brother (Henry the Lionheart) would sit on her.
My wild one, I'd be afraid she would have a heart attack just from the pure stress of having her carrier jostled around from travel. She takes cues from her sister on how to react to things in the world around her. Ex would have taken her, but he knew she could not get along with her sis. They are a package deal and stay together for the wild one's sake.
Two of the others though, may actually like the car ride and will find such joy in screaming at the mountains. They are joyful that way with no fear of the big wide world. How could I possibly think of letting them miss on the best days of their lives EVAR?
Sis will scream "OMG HAVE YOU SEEN THE MOUNTAIN!" and wild one will respond "NO, IT'S EVIL MAKE IT GO AWAY! IT'S GOING TO EAT US AND BELCH OUT OUR INNARDS. RUN!" (Yes, she is a bit neurotic)
Heck, this could be good training for my golden days when me and the young uns decide to quit the corporate world and run free naked along the beaches every day.