We have a GSD girl that will not let us leave the house without first verifying that we aren't going camping. She's too funny. She knows when I grab the "other" set of keys. Or, when we go in and out of the house too many times in a row...she starts getting suspicious. Once she does, she lays right at the door to the camper and you have to step over her to get in. Her way of assuring that she isn't left behind.
You've gotten some great advice above. Our philosophy is that Dharma (GSD) doesn't have any option other than to behave. I'm not the dog police, but something you typed sounded like a clue to me that maybe you aren't in control? You said something about her choosing not to listen at times? Not sure what you meant by that, and I may have misinterpreted, but we believe you have to be ABSOLUTE in your consistency and expectations of a GSD. We have been, and I can promise you that even with her highest temptations, I can snap a finger from hundreds of feet away and she WILL stop dead in her tracks and come back. Dogs, especially GSD's, need these unwavering expectations. You can't ask them not to get on the sofa and then cheat from time to time. A rule is a rule is a rule.
Hope I don't sound soap box like? Don't mean to. I see so many camping dogs that haven't had these expectations set. Usually, this leads to profiling in the GSD. It happens all the time, comments will be made if she barks even once (usually to get your attention to play). The little toy dogs can be yapping all weekend and no-one says a word. Be prepared for unfair attention in this regard.
Your GSD must be raised in the conditions you want it to behave in. If that is camping, then take him all of the time. Practice makes perfect. :)
So, what are some of our routines? She travels in the truck with us. She's a great traveller. She curls up on the floor and we don't hear from her again until the truck stops. She spends most of her time on a tether on our campsite. As she is older now, she lays down in a nice spot and hardly ever moves. She used to be irate towards other dogs, but doesn't give them attention anymore. If we leave the campsite, we put her in the camper and close the bathroom and bedroom doors. We've never returned to anything disturbed. At night, she sleeps on her pad right at the door. We do bring a wire kennel with us. There have been times that she is in that, which she doesn't mind, but it is rare anymore. I think it was more helpful when she was young and had more energy.
Anyway, bring him! Be a good parent!
Here's one of my favorite pictures of Dharma on a beach trip with us. You can see the "happy" all over her face!