We tried crates but our Coonhound mix puppy (9 months) howls the entire time... I mean the entire time. My wife had to sit with him in the backseat and he still howled. It was not until he was free that he stopped. Layed down and slept.
Our Lab (8 years old) has never been crated so I would not even know how he would react. Our little Coton puppy (6 months) is a lap dog so he just hangs out on my wife's lap or down by her feet.
We have yet to travel or camp with all three dogs. I've camped solo with our Coonhound pup. My wife and I camped with our lab. The Coton is too new to the family to have camped yet.
That being said, I am strongly considering the Canvasback setup that so many of you have recommended. I was thinking about those metal partitions, but the canvasback might be a good solution as long as they don't try to jump over or through it.