Okay, I'll be the bad guy here. Steveo scratched the surface, but backed out at the last minute. You, my friend, are 2,300 miles from Yellowstone. You have 5,000 miles to drive including a little running around. It simply cannot be done in 14 days and make it a "once in a lifetime" trip.
First, ignore the Utah visit advice. It should be reserved for the next "once in a lifetime" trip. It is worth the time!
Second, ditch the visiting friends in wherever. Friends should not be visited on your kind of trip. Your kids are going to frown on "you and good ol' Frank talking over old war stories."
Third, get in that RV in Raleigh and don't slow down until you get on the other side of Minnesota. Not that there isn't something to see along the way; there certainly is. But all of those places are within driving distance most any other time. You are going on a once in a lifetime trip, in only 14 days, and you want it to be "once in a lifetime" for all the right reasons, not because your angry wife left you in Nebraska with no cash and an empty gas tank.
I vote along the lines of South Dakota, Wyoming, maybe a quick clip into Montana and Idaho while that close, and then make a mad dash home.
I also think you need a minimum of seven more days for this trip. Have a GREAT time!
