Lots of good advice, my wife and I (both retired since 2006) have been to the GC 4 times. My experience is to stay at Trailer Village on South Rim and use the shuttle. Attend Ranger programs and enjoy the information about the GC that is offered. Maybe geology, wildlife, and early explorers will get old quickly for a 12 year old. We have flown over the GC by helicopter and got the CD of our flight, rafted for 6 days thru the GC--the best and most expensive way, and stayed 2 different times on the North Rim, as you can see we had the time. With less time, then recommend 3-4 days on South Rim, drive around to the North Rim for 2 days and then head to National Parks in Utah.