Thanks for all the helpful info guys, especially you Underdog. Sounds like you are the most experienced and I think we'll take your advice and not Muni in the grand canyon but might consider bringing them anyways for riding around Flagstaff/Sedona.
Now a question or two about not Muni'ing, but the Grand Canyon. Should we just go there and see it and not venture down into the canyon, or is it worth it to hike down some of it and back up it in a day (I know you can't go all the way to the river and back up in one day), but is it worth it to go halfway down or 3/4 of the way down? I think we'll only have one day to spend at the canyon, so what would people suggest we do? Thanks in advance for any advice!