Los Angeles Police Museum

With a few exceptions, this place is an interesting and fun spot to take kids. There's an audio-guided tour that leads you through the old police station, and there are squad cars and a helicopter in back that they can actually climb around in. Be aware that a few of the exhibits (Watts riots, etc) may not be appropriate for children, but it's pretty easy to steer them to what's age-appropriate. I thought it offered up an interesting history of the LAPD.