Our family took a trip to Vegas. We also have family that lives there, so it was another reason we went. I agree with many that the strip on Vegas is not for kids. We mainly did activities off the strip, stayed at the Cancun Resort (off the strip). There are tons of activities off of the strip that are family oriented (just like any other major city) that we couldn't do at home. The only thing we did on the strip was take the kids to the Tournament of Kings dinner show at the Excalibur. (Our kids are older, it could be scary for little ones) They loved it!
You must do alot of research before you go. Vegas websites and Tripadvisor are good places to start.