I also live in the Central Coast area.
Since lots of driving doesn't bother you, I would take Hwy 1 (PCH) for as much as you can. I actually love the section of 1 that goes from Gaviota through Lompoc, because it takes you through Rancho San Julian, which is one of the few remaining large ranchos in the Central Coast. 101 is also lovely here, but I like that stretch of 1 a lot.
Santa Barbara has a classic Mission, but I really love La Purisima mission in Lompoc. It's situated on agricultural land much as it would have been when it was operating, and it's a really cool park.
Hwy 1 is a stunner and well worth the drive, but it is slow and twisty compared to US 101. Hearst Castle is fun, but be sure to make reservations in advance, as they often sell out (
http://hearstcastle.org/tour-hearst-castle/tour-tickets-pricing/). In that area, we are particularly fond of Cayucos, a tiny little beach town just north of Morro Bay( a bit south of the castle) and the really epic smoked fish tacos at Ruddell's.
I'd take 2 days for 1, and drive from LA to San Luis Obispo or Cayucos the first day (especially if doing a Hearst Castle tour), then go up to Monterey and visit the Monterey Bay Aquarium in the early afternoon. It is SO cool, and completely worth it.
From there, it's a short couple of hours (or several hours, depending on traffic) up to San Francisco, where you can do lots of San Francisco things. I think Air BnB might be a good resource for staying in SF -- it gets expensive fast.
From there, I'd either explore the Sonoma County coast, or head over to Yosemite for a couple of days. Yosemite is a pretty heavily visited park, so if you're going to go in May you may want to make reservations for a place to stay well beforehand. Then it's a pretty straight shot back down I-5 to LA (five hours between SF and LA on I-5). Or you could take a long day and drive 99w down -- that takes you right through the heart of the Central Valley's agricultural land.
I have not much to say about LA, as I spend little time there, but the pier at Santa Monica is fun, and Honey's Kettle Fried Chicken in Culver City is pretty awesome stuff.
Have a fun trip!