We are in the San Francisco Bay Area – not sure how far north you plan on coming. I can give some ideas anyway .
Starting a bit south – Santa Barbara is worth seeing. It’s about 2 hours north of LA. Fog can play a role in the weather so sometimes afternoons are nicer.
Solvang – a quaint Danish village / town. It’s north of Santa Barbara – maybe an hour north. It is Typical of a Scandinavian town in Europe. Make sure to eat some Danish’s while you are there! You could see the whole town in a few hours, but it does make you feel like you are in Europe.
Monterey – home of the popular Author John Steinbeck , cannery row, Monterey bay aquarium ( we love it!) Monterey is about 2 hours south of San Fransisco.
San Fransisco – I could go on & on . So many things . The academy of arts & sciences is really good. If your kids are older there’s the De Young Museum , pier 39/ embarcadero, Ghiradelli square ( chocolate) , The zoo ,the trolley / cable car rides etc.
YOSEMITE !!! Is a must !! I am amazed every time we go. Make sure to hit the valley floor & take it all in. Although you said you would be coming in the fall. October can bring snow. If the weather holds up you should try to squeeze it in. Check the parks schedule too…..not sure how late in the season they stay open. We always go in the summer.
Hope this gives you some ideas !! Have fun planning your trip!
Jamie