I always buy such guards for my cars. I managed to find some clear rubber plastic ones from the local car spares shop for 2 or 3 quid and you can hardly tell they're there. I'd always prefer to have them than marks, chips, dents all the way down the door.
I've attached that super large bubble wrap to my garage walls and that does a good job. It doesn't stop the restaurant walls though and there's your problem.