That is going to be a busy trip, stopping and visiting with family. From Missouri to Wyoming area, you can expect many nights to be below 0*F during December and January. That can be challenging in a truck camper, traveling or camping for long periods, in below 0*F temperatures. Having a TC for a few days use, then not using it allows it to rid itself of humidity. Plus dealing with freezing food supplies, water. But you obviously know this, by the route and time of year chosen to travel. Also, plan ahead too in where you are going to stay, as many campground locations will be closed for the winter season, if you plan on plugging in during your overnights.
Suggestions of what you might be interested in seeing and locations would be a help too.
Have a great time!
b