Somehow I can not figure out how Yellowstone, Estes Park and Denver are the Southwest U.S. which the OP asked about. I believe they can make Arches NP in three days of reasonable driving. As I said earlier, Arches, Canyonlands, Monument Valley and Antelope Canyon are all close, less than a day's drive from each other. The Grand Canyon is about a half day drive from Page including stopping at the various overlooks coming in from the East Entrance. We found that 2 1/2 days in the Grand Canyon was plenty although we do not hike at our age. They should be able to get back to Southern Indiana in four days from the Grand Canyon. Assuming two weeks is actually 16 days with the weekends, 7 days driving and 9 for visiting the parks.