I would stay in Cambria for the visit to Hearst Castle and Morro Bay.

It is interesting to compare the SB Mission with La Purissima.

Santa Barbara to San Simeon is nearly 3 hours each way. I personally wouldn't use SB as a base for Hearst Castle.

I agree with janisj. I grew up on the Central Coast, smack in between Santa Barbara & Cambria.

Your trip is kind of all over the place. You want to stay in SB, but visit Hearst Castle, etc. Then drive south to San Diego (a 6 hour drive!).

What do you want to see in La Jolla? Golf? I think LJ is mostly a residential town. It does have beaches, but SD has nice beaches. Have you ever been to the SD Zoo? I know you said "no parks" but the zoo is quite exceptional.

If you want to see Hearst Castle & Cambria, then I would stay there. I think Cambria has some nice B&Bs to stay at. Or stay in San Luis Obispo; it's a nice college town & if you're there on a Thursday night they have a GREAT Farmer's Market that runs year round (I think).

From San Luis Obispo to San Diego it's easily a 6.5-7hr drive. You can drive all day and never leave CA.

You may want to geographically focus your trip more and leave out Hearst Castle. Santa Barbara has missions; and I'm sure you can find a winery (or several) to visit.

Just my thoughts.

I'm intrigued by the "one vineyard, one mission" - why just one?

If you're staying in Santa Barbara, then there's "one mission" right there. Otherwise, La Purisma is definitely the best mission to visit to get an idea of what mission life was like. There are only two of the missions that are not still in the hands of the Catholic Church, La Purisma is one of them and is a State Park set up for visitors.

http://www.lapurisimamission.org/

If you're going to visit "one vineyard", do you have a particular vineyard in mind?

Agree with the others that staying at least one night at/near Cambria is better if Hearst Castle is one of your destinations.

La Jolla is nice for a visit, but you probably want to be closer to San Diego, especially the DT area, for the restaurants and for the other sights.

Also intrigued that you don't want to visit any museums in San Diego because there are any number of smaller museums in Balboa Park, like the Railroad Museum, which your son might be interested in.

http://www.balboapark.org/in-the-park/museums

Is this a solo trip (one driver)?
Personally I would stay in the LA area overnight after your cross country flight and take the 10:20AM Coast Starlight from LAX (Amtrak) to Paso Robles. Rent the car there to visit Hearst Castle, vineyard and Mission etc. Take the train back to Santa Barbara if you want to see the city and colleges. Lodging can be quite expensive in Santa Barbara.
If you decide you like the train, you can get to San Diego and then rent another car for the remainder of your trip.

Travel from LAX to hotel . . . travel from hotel to Union station . . . Train to Paso Robles . . . Rent a car . . . drive around the area . . . return car . . . Train to SB . . . train to SD . . . rent another car . . .

Yes that makes sense (not)

Not only is that very complicated and inconvenient -- it would cost more than just renting one car.

That's a lotta driving... and apparently in winter since you mention skiing at Big Bear.

You'll be landing at 9:50 pm (East Coast time). If your flight is on time and you check your luggage, you'll be lucky to hit the 405 by 11:00 pm and arrive Santa Barbara by 1:00 am (again, East Coast time) or later if you choose to stop for dinner. That would be too ambitious for me unless I was familiar with the drive and the location of the SB hotel. You might consider taking a connecting flight from LAX to San Luis Obispo (less than an hour) which would put you much closer to San Simeon, Cambria and Morro Bay. There are also flights from LAX to Santa Barbara (30-40 minutes).

We do have winter weather here. When it rains, traffic slows to a crawl. And if it rains while you're here, your drives will take longer than normal. (We get almost all of our rain for the year between December and March, although Twentynine Palms gets little precip.) The Highway 18 portions of your drives from Joshua Tree to Big Bear and from Big Bear to L.A. can be impacted by snow (in a good year) and by weekend traffic. Chains could be required.

You'll be near missions at several points.

http://www.missionscalifornia.com/missions_map.html

Not a good plan, gotta re-think it. And by the time you're in your rental car it'll be 10:45pm east coast tme, are you sure you'll be up for a two-hour drive?

A few updates....

Thinking of ditching Joshua Tree and staying the first night in LA (where - should we stay to get away from the airport and get a head start on driving north?) and then adding the extra night to get up to Hearst castle and area between San Simeon and Santa Barbara.

I mentioned one vineyard because we are traveling with my kids and 12 and 9. Once its interesting after that they will be very bored. Same for missions.

For San Diego - researching staying downtown at either the Hotel Indigo or Solomar. We will have a car, but we do like to walk when we can. We want to definitely see the Midway ship and museum. The zoo is a maybe. Sea World and Legoland are definitely a No.

For LA - friends told me to stay in the Santa Monica area - any comments on that?

Is your arrival at 6:50pm a Friday night? Because Sat or Sun morning you don't have to worry about driving out of L.A. as long as you leave early. And you'll probably be up early since your east coasters.

Santa Monica is a lot of fun. There's plenty to do and you can walk around a lot. You can get to the pier and Pacific Park, which has rides and carnival booths, and no admission fee, although you do pay for individual rides. The Third Street Promenade is a great place for shopping, eating and people-watching, and there is a long, beautiful beach. The water is chilly and the air can be cool too if there is fog. The kids will enjoy being in Santa Monica. Do stay as close to downtown as you can.

Marina Del Rey is a good place to stay-very close to LAX, allows you to head north, first cycle around Venice Beach. Santa Monica is also a good place to stay before heading north from LA area. And while Santa M. has nice pedestrian shopping when I was there last summer I didn't 'get' what the big deal was about the pier-seemed quite seedy to me!
Def go to Hearst Castle! San Luis O is a great town to stay in. Santa Barbara waterfront is lovely

Any comments on where to stay in San Diego?