One day I would love to go to the Grand Canyon, but part of me is afraid to and I could live without. Although, I know for certain I would never go with small children as it seems too risky. I would also not go in the summer months. I would think October or April would be better weather months. Then again, it depends which part of the canyon you would visit, too. I definitely wouldn't go during monsoon season.
I think some people when visiting don't calculate for the heat of the hotter months or the dangers of ice in the winter months and the rapid temperature drops after the sun goes down.