Henry, my friend and I last February looked at these lookouts by starting in the afternoon in the east end of the Canyon. We stopped at evey lookout and finally did a sunset from Grandview. The next morning we came to Navajo for a sunrise. See both here http://community.webshots.com/album/39393383sWwDWH
Snow will help add contrast, but be prepared to be cold, as the wind often blows out of the canyon (and into your face). When we started walking to the edge that morn, we both said something about it being not too cold. Did we ever change our tunes after being near the edge for an hour or so.
I hope you enjoy your stay and get some great shots.