Sounds like a much better plan. Still roughly 4300 miles. Figure on adding a day or two going like a night under the stars in Badlands, you can spend several days in the Black Hills, add in Devils Tower for either a night or day (KOA is suppose to be good), and another extra day in the Big Horns mountains, finally after Yellowstone, spend a night or two in Grand Tetons. Dang, think I used up most of the 7 or 8 extra days you had and still need to get back home. Though don't worry, once you get into Nebraska, you aren't really going to want to do much any how plus we find once we have decided we are "turning for home", we really get moving to get on back.
Take on of those extra days and get home one day early. This gives you time to relax and catch up on the home things before you have to work. Plus it gives you the "Just in case" day.
