There are so many things to do at the Lake Mead National Recreation Area. Just making a stop at the dam is worth the visit. The new O'Callaghan-Tillman Memorial Bridge has its own parking area and you can walk across the sidewalk that runs on the north side of the bridge looking directly at Hoover Dam.
There are numerous hiking trails of varying difficulty. Renting a jet ski in warmer weather is lots of fun to do and gets you close to some beautiful rock formations. For those who live quieter lives, you can take the paddle wheel boat tour that lasts just over an hour. It can be a cooling and new way of enjoying Lake Mead. If you want to sit outside on one of the decks, don't go in July or August although the inside area is air conditioned.
Finally, for those who like riding bikes, the 35 mile River Mountain Trail runs along Lakeshore Road and is separate from auto traffic. Park at the Railroad Tunnels parking lot and ride north. Go as far as you want and then return to the car. It's a great workout with a wonderful view!