If you are a good sam member, use their (or Pilot, Flying J) to route your trip. It will give you gas stations, rest areas, eleveation changes (though it won't tell you what they are without actually buying the book) all in one nice printout. It will also tell you good sam service centers and campgrounds if you opt to take advantage of their roadside assistance. I saw someone mentioned that, but I can't stress the importance on not relying on your generic car/truck/insurance roadside assistance. Make sure you have something that will cater to RVs. I broke down in may 600 miles from home, and it was much less stressful to make a call that coordinated my towing (flatbed for SUV/ separate truck to tow the trailer), arranged the service station, etc. than it would have been if I had to figure that stuff out for myself, or try to get my regular insurance roadside assistance to do it.
You also might want to consider 'surprise' bags for your kids (even if they are older). They help us a lot with road boredom...I get a few new movies, DS games, download some stuff on my phone (family travel games), rubik's cube, maze books, etc. Really, really helps us, and especially helped us when we broke down.
We also use our toilet on the road quite a bit (#1 only lol), and put paper in a scented doggie pick-up bag. For smaller kids it's a LOT easier when rest stops are filthly. I put a bag of ice in the tank when we leave, add the blue stuff, and keep a water bottle of water from home (I carry no fresh water to keep weight down) to pour down on the flush if needed.
We also grab the cracker barrel locations in the event we need to sleep (our trips are 13ish hours, and we sleep at cracker barrel at night - RV friendly, but no trucks).