No, the Grand canyon is not too far away.  Short side trips to Kolob
(between Cedar City and Hurricane) and Pipe Springs (on the way from
Hurricane to the Grand Canyon) may be interesting--they are right
off the highway.  Pipe Springs (a small fort) gives you real insight
into just how the pioneers lived.  You have missed one major must
see attraction--Cedar Breaks in the mountains above cedar city.
Take lots of film--they have a reason for calling this kodachrome
country.  Natural Bridges in the four corners area is also very
scenic, but may be too far off your route.  Monument valley is
spectacular, but again may be too far away.