Cedar Breaks, just outside Cedar City more or less, is a wonderful place and I would suggest you go there instead of Zion Kolob Canyons. Cedar Breaks, especially near sunset, is absolutely beautiful. I think you'll really enjoy it.
Check out http://www.nps.gov/cebr/index.htm
the national monument's site for information.
I've a few photos on my website at http://ncsparks.com/southwest-trip/cedar-breaks.php
to give you a flavor of the place.
When we were there in September 2010 we found Cedar Breaks more interesting than the Kolob Canyons area of Zion.