would you recommend the car hire/stay the night route as well then?
Just to expand a bit on my reasons for recomending this, the major advantage is that you can take things at your own pace. On the way up you can stop off and have a good nose around the hoover dam and then pop across to Seligman which is the town at the start of route 66 which is suposed to be th inspiration behind radiator springs in the movie cars. Then when you get to the canyon you can spend as long as you want at the bits you want without the pressure of the ticking clock added to which you get to see sunrise and sunset which are turly spectacular and don't come with the day trip. Finally you get to go on a bit of a road trip which is a US tradition.