We've stayed at Newport Dunes many times, and it's great for a last-minute beach vacation especially when most state beach campgrounds are booked out way in advance.
There's a nice bike trail that circles around the bay, which is great for kids. Also, lots of amenities for families, including playgrounds, water toys, movie nights and fire pits. The convenience store sells RV supplies, snacks and beer/wine. You can ride your bike to Balboa Island across PCH, spend a day at Fashion Island shopping center, or drive to the beach.
A few cons: The beach is not exactly close. You will definitely have to drive. And the bay can sometimes get stingrays. Finally, the campsites do feel a bit like a concrete jungle with few trees and very close proximity to your neighbors.