I would recommend considering East Shore RV Park
(full hookups with spacious lots) - it certainly doesn't feel like LA and seems like its above the smog line. Nice and grassy, has play grounds scattered around, a lake for fishing and water sports, and lots of walking trails. As it is a county park, there are rangers checking access so it is very safe and secure. When we were there, people from LA come up with their kids to get-away from the hustle-and-bustle, but it isn't so far you can't get to the various LA highlights (Disneyland, Knott's Berry Farm, Universal, La Brea, beaches, etc.)! Although it is a 7+ hour drive for us, any time we're in the LA area, this will be our campground of choice.