I know some people think LV is no place for kids, but my 6-year old son loves it there! He has been many times, and is always asking to go back. First of all, the handing out of pamphlets isn't as bad as it used to be, as LV has really cracked down on making sure they don't leave the stuff all over the sidewalks anymore.
Someone suggested the Pirate show....at TI. Don't do that, 'cause it's not geared toward kids any more. The people are pretty scantily clad now. Circus Circus is always fun. The Mirage...although I'm not sure they have the white tigers there anymore. But the entrance is so cool for kids to see. Going in and out of all the casinos is a blast for kids because of all the lights and sounds. The Fremont Experience in downtown LV is a must for kids.
My son and I go hang out, walking up and down the Strip, checking out the Nascar, M&M's, New York New York, the mall (especially the outside of it where they have the led displays). You can go to Harrah's, and stand outside the outside bar, and watch the bartenders do their tricks "Cocktail" style.
And then if you want to spend time on your own, there are hotels that offer services, although you'll need to stay in the hotel, or I use a sitter sometimes, who is highly reliable and very, very good.
Oh, and go up to the top of the Stratosphere and look out! Both day and night! Most of all, just have fun.
As for the Hoover Dam thing, young kids aren't really into that in my opinion. I am very active with my son. We go to so many museums and amusement parks, farms, beaches, etc, but I'd never think of taking him to Hoover Dam. It's a long drive to go see some water rushing off some concrete. It's not worth the drive for kids, unless you're going that way anyway.