Are you looking for fastest/safest route, or are you looking for some sight-seeing opportunities?
If you're sightseeing, take a look at
1Z1 located inside the rim of the Grand Canyon for a
great B&B at the Bar Ten Ranch (room, steak dinner and huge breakfast = $110/person), then a stop at
L06 Death Valley Airport. Plan for a stop at
KUAO Aurora Airport for a tour of Van's Aircraft Factory.
You can see my trip write-up for Bar Ten
here.
For the return flight, consider flying from Seattle to
KJER for cheap gas, then fly down the Wasatch Front (mountain range directly east of Salt Lake City), and then over to Leadville
KLSV. Leadville being the highest elevation General Aviation airport in North America, Death Valley being the lowest elevation. Leadville has a couple of Jeeps for airport courtesy cars (keys in the usual location - out in plain site), and there's a great variety of restaraunts just a few miles up the road in town.