Dont worry, I pet him so much before I had to go and after I got back. He's a very very good boy... Even when he throws up on my bed for no reason while surrounded by perfectly good hardwood floors.
Just keep them on a harness. They'll get used to it.
I've had cats that I would gladly take camping, even without a harness. My old guy Jake would have LOVED the woods, and I'd never have to worry about him getting lost. He'd would have wandered far, but he'd always be able to find his way back to the campsite. He'd have had no interest in running away.