Wild idea: spend the whole vacation in the high country of Colorado. A lot closer to Missouri, cool, green, lots to do.
The most important part of a camping trip with teen-agers is the time spent just hanging out around a campfire, playing board games on a rainy afternoon, throwing rocks into a river, chatting while hiking, etc. Not driving, while the kids are engaged by their tablets and are tuned out. Not hustling to pack up and leave yet another campsite to hit the road, while everyone is focused on their chores, rather than interacting with each other.
It won't be long till they are grown and gone. (Don't ask me how I know this.) . Every minute of "kid time" is precious.