You did not say when you were doing ths trip. The Monarch butterflies can be seen in Los Osos near SLO and also in Pacific Grove (a very scenic little town right on the ocean near Monterey- save your money by skipping the 17-mile drive through Pebble Beach) in the winter months when they roost in great numbers. Check the State Parks link given to you by a previous poster, or simply Google.
While you're Googling, check on the winter months when you will be able to view 100s of elephant seals lounging on the beach close up, right next to the Hwy. Their haul out place is north of Hearst Castle, and south of Piedra Blanca on Hwy 1.
If you take Hwy 1, make at least a short stop to view the waterfall at Julia Pfeiffer State Park that cascades into the ocean. (also rainy season to late spring).
There was an extensive fire at Big Sur in June. Once the rains start, I would expect that Hwy 1 might be subject to closure due to mudslides. Big Sur is usually a favorite overnight stop. There are a few good little restaurants along the way.
North of Sta. Cruz, Big Basin and Henry Cowell State Parks have coast redwoods.
Be advised that commute traffic through San Jose on 101 is also brutal.
Hwy 17 from Santa Cruz to 101 south of San Jose is not for night or rainy weather or commute driving, nor for the faint of heart.
If you are over 65, you are eligible for a senior BART ticket for transportation to and within SF. For $8/9 you get $24 in rides. Each person needs a ticket. You can't buy these at the BART station. (Go figure) The place to get them is any major GROCERY store close to SF. Just ask at checkout or customer service. Newstand type stores in the City sell them. Depending upon where you're staying, you might be able to catch the hotel shuttle to the airport and take BART from there. (subway/metro) Parking in SF can be up to $20/hr.
There are 2 newly rebuilt museums in Golden Gate Park, the De Young (art) and the Academy of Science (Google this - check out the rainforest and the living roof). I've heard about a new Museum Shuttle that takes you from one museum to the next for about $7.
If you'll be traveling in Dungeness Crab season - usu starts before Thanksgiving, stop at the fish shack in Pilar Point on Jwy 1 near Half Moon Bay for crab or at least fish & dhips. Sinch DH likes fishing, he would probably enjoy checking out the fishing boats, though this has not been a good commercial season so far.