Hoffbrew -
With the kids, you probably could not have picked a better campground. The Grand Canyon Railway is just right there. The steam whistle will give you a 5:30am wakeup call.
Be sure to get your tickets well in advance before arrival - you WILL want to ride the train. Otherwise, you will be driving in and parking to take the shuttle around South Rim. The new Science and Resource Management Building was just dedicated on January 15. Hmm, I'll cut this short and just say, visit the NPS website:
http://www.nps.gov/grca/index.htm and explore everything.
A couple more items though: There is a Chase Bank at South Rim next to the grocery store. Across the road from the bank and store, just a short walk back into the woods, is a cemetery. If you live at Grand Canyon, when you pass you can be buried at this cemetery. Look for the grave of John Hance. This crusty early explorer, miner, and resident of Grand Canyon actually "started" Grand Canyon tourism and mule rides. Hance was given to "tall tales". To explain the Canyon, he told visitors that he dug it himself with his shovel and pick, and see those mountains south of the Canyon, that's where he piled up the dirt! If you want to do the mule ride, get your reservations in now! (Links to Xanterra's services on the NPS website.)
Be sure to take some time to visit other areas around Williams and the Canyon. Take in Sunset Crater Volcano National Monument and Wupatki National Monument northeast of Flagstaff.
http://www.nps.gov/sucr/index.htm This volcano erupted some 900 years ago, and one lava flow engulfed a Mogollon pueblo. If you get to a clearing while climbing Sunset and look west, you can see San Francisco Mountain - and if you look towards Humphreys Peak, you will realize that this volcano had the same type of eruption as Mount St. Helens, only this eruption happened some where around 100,000 to 400,000 years ago.
There is also a great presentation about the Fred Harvey Company and the Harvey Girls at South Rim. Be sure to take that in! And take some time to drive out to Desert View Tower! The view of the eastern part of the canyon is quite impressive from the top of the Tower.
Send me a PM if you would like more. As you can tell, I'm quite fond of the Canyon and this part of Arizona. Kinda goes with geology
. . . And if you do enjoy yourself, consider joining the Grand Canyon Association which helps fund the projects at the Grand Canyon!
Ron