Definitely worth considering Antelope, I was there just before noon and was able to capture the sun streaming in.http://www.flickr.com/photos/filipmakowski/6158291826/#in/set-72157627571758317
The biggest challenge is that at any time when the sun is coming in you have over 200 people in the canyon across 10+ guided groups. I had to take this photo handheld at ISO1600, f2.8 with the 16-35mm II (which I have never found to lack sharpness) as there was absolutely no time or space to put up a tripod.
Suggestion for Grand Canyon: hang around after the sun sets, you may be able to get some great shots with iridescent clouds. When I was there everyone had returned to their hotels just after the sun had set, missing the opportunity for what turned out the best part of the evening.