I wouldn't recommend co-sleeping in the same bed, there are dangers associated with it (http://www.parents.com/advice/babies/sleep/is-it-safe-to-let-my-baby-sleep-in-my-bed/), and it isn't a good long term solution.
You might look for a portable cradle of some kind which can fold up for easy storage or transportation. I don't know how large his current cradle is, but is it possible that you could put the portable inside the larger cradle? That might help him get used to sleeping in it.
Another thing you might try is to arrange his bed so that part of it is portable. Lay a blanket over the bed, and make sure he always sleeps with that blanket against him. Before you go on vacation, make sure he has slept on the blanket for a week without washing it, so that the scent of it is familiar to him. Babies are soothed by familiar scents (http://www.parenting.com/article/your-babys-sense-of-smell). So if you put his blanket down on whatever bed you are trying to get him to sleep in, it might help.
I was a little confused...are you saying that you want him to sleep in the car seat but he refuses, or that you want him to sleep in your arms on the ride home and he doesn't want to?
Infants are usually soothed by the vibrations when riding in cars...my sister and brother have a couple of kids who don't want to go to sleep so they used to drive them around in the car until they fell asleep, then they would carry the car seat into the house and place in the child's crib for half an hour. Usually then the child will sleep through a transfer to their bed.
Once you get your child used to sleeping in a car seat that will help with any kind of travel. We used to take our car seat with us when we went travelling, even flying. The familiarity of the car seat helped our daughter to fall asleep in a strange car, and we put her in it inside the crib our sister provided.