I prefer hiking in Valley of Fire to Red Rock, but both will be too hot in August. I just did a trip report on hiking in Southern Utah, but that's much too far for getting back to Vegas for nighttime shows. And August is when there is a greater chance of flash floods in the canyons. Can you delay your trip and go in the fall? The aspens changing color make it quite nice then. An option would be to spend a few nights in Bryce and Escalante and then a night or two in Vegas on each end. (I finished my hiking off with a much-needed day at the spa at Trump.)

If you decide to go to Escalante, Kiva Kottage is surely the nicest lodging in the area.

There are some photos here from my trip:
http://www.flyertalk.com/forum/trip-...te-w-pics.html