With kids, Knott's Berry Farm (Buena Park) works.
The LA area's value coaster park, but the real differentiator isn't price — it's character the bigger parks don't have. Ghost Town, the original 1940s Old West district that the whole park grew out of (it started as a berry farm with a chicken-dinner restaurant and a replica frontier town), still has genuine boysenberry-everything, a stagecoach, and a panning-for-gold corniness that's weirdly charming. And the autumn Knott's Scary Farm is the oldest and one of the best theme-park haunt events in the country. Come for the Old West texture and the Haunt; the rides are good but it's the personality that separates it from a generic Six Flags.