Class C vs Trailer for Cross country with family? Help

Because of the difference in an RV vs car driving, a good rule of thumb for RV'rs traveling is 50 miles in one hour. AND, you should include about one hour per 6 hours of driving for fuel and potty, lunch breaks. And, lastly as mentioned, with a truck everyone should be belted in for safety. A Class C, they probably won't be in a seatbelt down the highway. So, just for safety's sake, a truck and trailer (5th wheel or Travel Trailer) would be best. Good luck and either way, the kids will remember this trip.