I highly recommend The Venetian in Vegas. You can try hotwire.com
as this is the ONLY 5 star hotel in Vegas offered on hotwire.
So if you choose 5 star hotel - it has to be The Venetian.
If there is no convention - you can get it for ~ $120/night
Summer can be very hot in the area, but if you could, try to
get a permit for the Wave -
http://www.wildlifeland.com/Canon20d/Wave/
by far the most amazing of all the Utah/Arizona desert places.
Bryce, Arches, Zion, Slot Canyons, Grand Canyon are all great.
Try to drive through Tioga Pass - it's a beautiful road through the Sierra.
You end up in Yosemite Valley.
If you have any questions, I'd love to help.