Thanks for your input, everybody! I'm saving these suggestions for this trip, and trips down the road if we don't get to them.
I've got the Dogfriendly guide to the West coming in the mail this week, so that will, I hope, steer us to cute outdoor cafes where they provide water bowls for furry friends, and to beaches where they can chase a frisbee and wrestle.
Looks like our first stop will be Snow Canyon State Park near St. George, UT or if they're full (they appear to be) the Zion Canyon Campground in Springdale, UT. Pups can stay at the Doggy Dude Ranch for a day while we hike, and then we'll load up and tow down to Williams, AZ to catch the train to the Grand Canyon (again, a little doggy jail time for the day).
From there, it'll be east or west. I think the weather may influence us a bit... we're craving warm weather but not super-warm. That may be all the national park hiking we do, as the pups want to sniff out some trails.
DH wants to see at least one MLB game. That would take us west, as the Dbacks aren't at home until April 7, and we plan to be back in Wyoming by April 9. Oh OH unless I can get him to delay his gratification until the end of the trip, when the Rockies are playing at home on April 7-8 against the BRAVES!
(Being from Memphis, that's the only team I ever followed) That way we could go east!
Okay, I have decided absolutely nothing except to see which way the wind blows us.