Day, yes Vegas is pretty centrally located and close to tons of great stuff. The only real minus is that the Average daily temperature is like 156 degrees.
But in it's favor is the fact that the Red Rock Rangers are only one step down in ass-hole-ness from the Yosemite ones. So when you get to the Valley you will be up for dealing with them.
Watching Fat gamblers stuffing nickel slots, than hitting the 24/7 buffet is one of the highlights of any trip to the Red Rocks.