okay...
hmm,
well, if you can persuade DS to do Disney at the end of the trip I'd do that, and I'd reckon on two days on it (perhaps with some side trips if you don't want two full days). I find on road trips it is nice to have some freedom to make changes in case you want to have an extra day somewhere.
La Brea, my kids loved it. The bit they loved the best was poking a stick in a tar patch in the grass. They got tar on them. Don't wear nice clothes that day just in case.
Remember you will probably feel a little ugh the first few days, you might like some short trips like La Brea or the coast.
When my kids were younger we did a CA road trip. We drove up 405 after rush hour (the 405 is called that because you get to do 4 or 5 mph at busy times). It only takes 2 hours from LAX if you miss rush hour. Stayed in Santa Barbara overnight and spent the morning looking around and then went to Solvang for lunch. Solvang is cute but touristy but I like it anyway. It is Danish so have pastries. We found Bald Eagles at Lake Cachuma and a lavender farm at Los Olives -- both of these were 10 minute stops to let the kids out of the car.
We planned to overnight in Morro Bay but when we stopped (and let the kids have garlic oysters for the first time and watch the sunset over the water) we decided to continue to Cambria which is the gateway to Big Sur AFTER stocking up at the local supermarket. Big sur is expensive and not a lot of shops, take lots of snacks etc. The beach there has black sand and was gorgeous early morning while my DH slept in. Fill up with gas.
From there we started up Big Sur, you need a good long day to do it justice but it is BEAUTIFUL. We first stopped near San Simeon to see the elephant seals. Kids really enjoyed this, it was busy and windy but my youngest loved listening to the warden talking about the seals.
We skipped Hearst Castle because I felt my kids were too young and we did not have enough time.
Next we stopped at Julia Pfeiffer Burns State park, if there is parking free then stop (if not do next stop and come back). Google it. Seriously. The view from the looked out is breathtaking in a kind of hollywood stranded on an island with some hunky guy breathtaking. It is a waterfall falling on the most gorgeous beach with turquoise water. You can't go down to the beach but you will stand and look and go wow. Take warm jackets, the other side is amazing craggy coastline with turquoise ocean and an amazing amount of wind! Then walk back along the trail to your car and eat a picnic sat in the woods while your 5 year old plays in the stream. If you are like us you will plan to stop for 1/2 hour here and stay 3 hours instead while your kid and husband play in the water under the trees.
A little further on is Pfeiffer Beach. An AMAZING kid beach, you can't swim but it is stunning and has sand to dig with.
Next fun kid thing was Bixby bridge. V. windy but they were wowed at it.
From there we drove and drove and drove until we hit Monterey (it was getting dark). Either stay here or drive onto Santa Cruz if you have time.
Monterey and Santa Cruz have some fun stuff to do but we wanted to hit Napa so we pressed on. If you don't care about that either spend some time there or go to San Fran. We have done San Fran a number of times so we didn't stop there this time -- plus we could loose our kids for weeks (I'm very serious) at the Exploratorium so it is somewhat dangerous to stop there. If you do go there spend a few hours in Berkeley at the Adventure playground. It is a kid heaven, a playground built by kids. At 5 he is a little young but allowed if within arms reach. We drove over the Golden Gate bridge and stopped on the Sausalito side to take pics as my youngest really really wanted to do that. We had an expensive italian dinner in Sausalito before heading to wine country.
We spent a few days in Napa/Sonoma with friends and touring a vineyard/winery and other stuff (pubs for DH) before going to Sacramento (visiting friends, Old Sac and State capital, fun but probably not your best use of time.
On the way home we spent one day in Yosemite, really a little short but we had a lot of fun. Try to stay nearby the night before so you can spend all day there. Go to the visitor centre and they will help you plan your trip. My kids spend most of the day clambering over rocks and getting wet in various streams. We chose not to see all the sights as they were having so much fun.
That night we tag teamed it driving in the dark to Fresno, it was a long ugh trip. Central valley can get a little monotonous even during the day time, it is one long flat agricultural valley (with few stops, even for gas). We stopped in fresno over night then drove out to Sequoia/ Kings Canyon. It is a bit of a drive but the kids liked the huge trees. We'd drive, stop for 5 and take a pic then drive to the next spot. Leave plenty of time for your next drive as there isn't much between Fresno and LA (including gas). We stayed in Pasadena that night as my eldest really wanted to see where his friend was filming a movie and he also wanted to see the holywood sign. We spent a couple of days in LA before heading home to San Diego!
PHEW! A long trip, but one the family still talks about.
If that doesn't sound interesting then let me know and I can tell you about the 7 state, 8 days one. It was hard work though, we saw a lot.