We drove up from San Diego to San Fransisco over 10 days - it was a lot of driving! We flew past LA so didn't see a lot there, but stayed at some lovely places along the way. Would definitely recommend a couple of nights in San Diego, its lovely there.
SD wasn't somewhere I'd really considered as somewhere to visit before that, and we originally wanted to fly into SF and drive down the coast but the flights worked the way round.
San Fran was really cool, he'll love Alcatraz but maybe watch the movie Escape From Alcatraz before you go so he knows what it was all about. We watched it while we were there and were glad we did as the tour obviously tells you all about how they did it. But yes definitely need to book.
We thought about adding Yosemite or Las Vegas etc but it added on so much more driving we decided to do it as a separate trip another time.
Also the weather was a bit changeable as we went in Feb, so Yosemite was actually snowed in, while San Diego was sunny and lovely.
For us it was mainly about food and shopping, so we basically planned our route following Trip Advisor's best diners etc along the way. Be aware that thieves target rental cars, as the license plates will show that you're not local. So don't leave anything valuable in your car while you're out and about. Obvs being a road trip, you will have all your stuff in the boot, but keep your valuables on you. We learned this the hard way 
resulting in a trip to the embassy to get a new passport for DP and the loss of thousands of £ worth of electricals he'd left in his rucksack in the car! luckily I'd kept mine in my handbag
Laguna Beach was beautiful, and the sealions and sea otters etc all along the coast were gorgeous! We even briefly saw a whale on a boat trip, although it was quite elusive!
We went without the DCs so not sure what there is specifically for children, but the aquarium at Monterey was great. General beachiness and lots of burgers may help too!