We just got back from the Grand Canyon a few days ago, and it was the first time Kim or the kids had ever seen it. It was cloudy and rainy most of the time, but it cleared up enough for us to see everything, and really, the clouds made it look pretty neat, and we got to see some great rainbows in Sedona. We had a really great 4 days.
We also went to see some amazing Indian pueblo ruins in Flagstaff,where there was a natural blowhole that blew air out of the ground, as well as a really nice museum.
One of the other highlights of the trip was hiking up a volcano to see the "Bonito lava flow".