JWalker,
It really depends on your comfort zone. If you won't mind the dog breathing down your neck and licking your ear while you're driving then just let it run free. Several things to consider. The dog will be different when it gets older. In general after the puppy stage they usually become more docile and satisfied just sleeping or lounging. Our Golden slept in a chair in the motor home and was just fine. She pottied when we stopped and never had an accident in the MH. All dogs need socialization to be well adjusted. When they are young expose them to as much and varied items, noises, situations, kids, and all kinds of other people, riding in a car etc. Our new dog spends much time in the garage while I build things. We started this when she was 9 weeks old. New sounds or noises don't ever bother her. She is a 6-month golden Cocker mix is not allowed off the leash. She's not house or chew broken yet and that's why. Even after she's house broken she'll get limited freedom for the first year or two. The crate or kennel concept is really great. It gives the dog a sense of home. They like the confined space for comfort and they usually won't mess where they sleep. She did once because the crate was to large when she was small. I had to put up a partition and she has not messed in her crate again. When she got bigger I took it out. After about 2 months we could safely leave the new pup from 6-8 hours in the kennel with no problems. One other very important thing to consider. If you are at a camp ground and your leave for several hours to sight see the dog will usually be much quieter if it's in its kennel. If it's allowed to run free to look out the windows it will notice every car, person, cat, dog, and person walking by and bark, bark, bark. We all know because we have all experienced it. With that thought in mind start using the crate NOW not later. Get the dog trained to use a crate every night and you and it will be much happier. We are heading to FL in a few weeks. We'll put the crate in the back seat and use it but some of the time we will also allow her out on the seat tied up. One more thing. Dog obedience school is a must. As owners we need to figure out just how to train a dog. About 13 years ago I took our golden. It wasn't the dogs that were going to school but the owners and the instructor told us that. Raising a dog is just like raising kids. Some of us figured it out, survived and raised pretty good kids. Then there's the other group.
TeJay