There are some Hotel/Casinos where you can check in and go to your room without ever seeing the casino. Red Rock and Green Valley Ranch come to mind. That being said, without gambling Vegas is a relatively cheap vacation destination and there are numerous things for children to do. As Sue mentioned, there is the Discovery Museum by the Smith Center. There is also Wet and Wild Water Park which just opened. During the Holiday season there are the lights at the Speedway as well as at Ethel M Chocolate Factory, The Shark Reef at Mandalay Bay, the Conservatory and Chocolate Fountain at Bellagio, Mac King's show at Harrahs, Red Rock Canyon, Hoover Dam, Valley of Fire, Grand Canyon Skywalk, Tournament of Kings at Excalibur, Race-carts, the amusements and view from the top of the Stratosphere, etc. You could spend quite a longtime here and not run out of things to do with your children. While I agree that the billboards driving down the strip with the "Girls that want to meet you" message aren't the most wholesome family viewing, there are many things in our Valley that are worthwhile and can only be seen in this area.
Larry from Las Vegas, NV