I recon'ed the North Rim area, and came to the same positive conclusions as the folks above. I had to 'stop short' during my last trip to Lake Powell, so I stayed at 'Lee's Ferry' N.E. of the GCNP Park proper. That was a really nice setting right on the CO River; very scenic.
Some recon tips to pass along are to 'fly over' the area using Google Earth. You can gain a lot of info that way, including size and setting of various Campgrounds. 'Trip Advisor', linked on the left of the Google Earth Webpage, has many down-to-Earth comments on Campground amenities; good/bad Food and prices thereof; and so on. The pic function 'Panoramio' on the Google Earth Webpage shows pix uplinked by Visitors, and gives a ground level view of different areas.
The lil 'x' icon reads out elevation at the Webpage bottom, so you can know what elevations and Topo changes you're in for, and/or crisp night sleeping conditions at higher elevations.
At the 'History & Almanac' section on the lower left side of this Webpage, you can put in dates from years prior to get some sense of Weather historically during a given time period...
Weather Underground ~ Grand Canyon National Park
Google Search Results ~ Grand Canyon