Here is a link to the NPS Lake Mead Campground website: http://www.nps.gov/lame/planyourvisi...nglakemead.htm
I agree with Glen Taylor. It will be scorching hot out at the Lake. I would only go if I had a boat. There is no grass at the campgrounds to pitch a tent on, it is dirt. You cannot be sure if there will be shade from trees so an awning is a must. It gets even hotter at the Lake and the Colorado River Valley (Laughlin, Willow Beach, Cottonwood Cove) than it does in Las Vegas during the summer.