May is a good time to be in OK as far as temperatures, but do keep an eye on weather forecasts because we can get some tornadoes in May also. Some have been doozies. You might like to tour the historic Coleman Theater in Miami OK. See the "world's largest totem" a bit west of Foyil and the Blue Whale at Catoosa. Shop the Bass Pro Shop in Broken Arrow. Tulsa has a couple of art museums, the Gilcrease and the Philbrook. See the round barn in Arcadia, and stop at POPS for the huge assortment of soda pop brands. OKC is home to the Cowboy/Western Heritage Museum.
For stopping and shopping, you might love Santa Fe and/or Taos for the art galleries and shops there. Then head north to Pagosa Springs, CO and soak in the warm springs there. Drive west past Durango and take a day to see Mesa Verde. Continue west into Utah on 491 and then north to Moab (this road has some amazing sandstone scenery). If the temps are not too hot, I would consider Arches National Park a must-see (allow a day or two here at least). If you are still game to go on north, make your way to the beautiful Tetons; either jog to the west and go through Salt Lake City, or take the shorter route north in CO on hwy 169, then to Vernal UT, Green River WY, and finally Tetons. If you tire of the mountain views, Yellowstone is a short hop farther north.
Now, I really would think twice about continuing to Glacier NP so early in the season. As it is, you will be in Tetons/Yellowstone at a time when night temps will be close to freezing and snow is quite possible (we got snowed on in Jackson Hole on 6/13/99, and you will be there weeks earlier!). Northern Montana can be pretty chilly and much of Glacier NP will still be socked in with snow; the beautiful Going to the Sun Road doesn't open until July. Forget Glacier this year and knock about 900 miles off your drive. Instead, I would suggest leaving Yellowstone and meandering east through WY (see Devil's Tower, perhaps) and into South Dakota, where you could visit the town of Deadwood and iconic Mount Rushmore. After that you may feel like scampering home by the shortest route.
Here is the big thing to keep in mind:
It is a vacation, it is supposed to be
fun. If at any time it stops being fun, change what you are doing! For example, if you find yourself tiring and wanting to head home early, do it. Or if you hear of someplace you hadn't thought of before to see, go see it. Don't sew yourself into a schedule that's hard to get out of, other than (of course) being back home when you must be home. Stay loose and flexible, relax, and enjoy the journey.
BTW, you can use maps.yahoo.com 'directions' feature to calculate trip mileage. Just enter starting point and keep adding destination points, and it will show a route on the map with driving time, distance, and directions. It's a great tool.
Mike G.
Liberty is meaningless where the right to utter one's thoughts and opinions has ceased to exist. That, of all rights, is the dread of tyrants. --Frederick Douglass
photo: Yosemite Valley view from Taft Point