I think a lot depends on your budget for hotels, and also do you want to stay by the ocean and then travel into the LA area? I will be doing the LA to SF trip next year, but I will be with my DH and 2 boys ages 20 and 17. We will be staying in Santa Monica, close to the pier as I think they will enjoy that..all the activity. We will be driving into West Hollywood. We might get bikes and ride to Venice Beach, if it's not too far.
We will be there 3 days, then start our trip north. We will spend the night in Cambria (and stay at the Best WEstern Fireside Inn on Moonstone Beach). We will visit Heart Castle, Elephant Rockery on our way up the Highway 1. When we get to Big Sur, I heard a great place for lunch is at Nepenthe..a must do. There is the college town San Luis Ospido that is north of Cambria, but we won't go there.
We will go to Carmel to see, and I've been to Monterey (just 5 minutes away). The Monterey Aquarium is very famous. Howver, we will stay in Santa Cruz instead of those two places. I think the kids would like the Boardwalk, and we will go to Henry Park for the Redwoods. We'll sort of do the sites for those 3 towns in 2 days or so.
San Francisco..also has Muir Wood for the Redwoods but I cliffs and you are on the edge of them coming down from Muir Woods...I think Henry Park is good enough.
There are so many things to do, it's overwhelming and I find I redo my itenaray regularly. Good luck and have fun!