A couple of observations.
You will likely be tight on time. It is easy to spend a week or more in California and not see much of it. The Pacific coast is not like the Gulf of Mexico. The cliffs, beaches, rocks and shoreline are worth the time to get to the coast and spend time at it. Second. California is huge. Driving distances can be long. It might be better to fly to California and rent and spend the requisite time where you want to be not two of the three weeks getting to and from where you want to visit. Other things or places to see in California is a dormant volcano at Lassen, Death Valley, Sequoia, Yosemite, Alcatraz in San Francisco, Lake Tahoe, Big Sur/Monterey and maybe some of the 49er gold rush towns if your family is into that history.