We have only stayed at one Wally World RV Park, and I did not like it. The rigs around us in the morning were not the same one that were there when we went to bed.
400-450 miles a day for 5 days will wear you out pretty well. But I agree that if you are just getting there, then there is no reason to stop driving at 2 o'clock in the afternoon.
Expect to pay extra for the second vehicle each night. Hope you have radio's to talk between the vehicles and cell phone's if you get separated. Set up a common contract to call if something happens! And remember that you have two drivers that will both be tired each evening.
Going through major cities, you can play leap frog to get into the correct lanes etc. Our first trip through Phoenix with the trailer was with another couple and we took turns letting each other "in" as we navigated the maze!
We plug in electric, drop front jacks, use park cable or bat wing for news, and try to leave the next day at around 8AM. 3.5 days from NW Washington the Gold Canyon, AZ - 1650 Miles. Usually stay at the same spots each year, as long as we do not have to go to the coast to get around snow on I-5 in Southern Oregon/Northern California.
Good Luck and drive safely.
Chris