A great fun Sunday hike for the family when the weather isn't too hot. Travel towards the entrance to the Lake Mead National Park but turn off before the entrance into a parking lot. The trails start from there and head along the rim of Lake Mead down towards Hoover Dam.
The tunnels are fun to walk through. I believe there are six in all and the total round trip to just the end of the tunnels and back is a few miles. You don't have to stop at the end of the tunnels. In fact, you can walk / run or bike all the way down to Hoover Dam. I have run a 5K race on this trail that takes you down towards the dam.
This is a dirt trail, so I don't recommend bikes for younger kids. Even though I see kids on them, I think some parts can be quite difficult.
Bring lots of water. My kids loved having hiking sticks with them.
Some people look for Geodes around here, but I have never done that, so I can't review.
Sometimes you will see wildlife, like the time when a big horned sheep came running down the hill by me, lost control and almost ran into me - or maybe he was just psyching me out! In any case, it was pretty cool!
Bring your camera and water with you.