Once you're done in the parks I'd head north to Lodi and cut across 12 (get gass)towards Fairfield. A little south and head up to Napa Valley for a day or two of wine tasting. Hotels are pricey but worth it. Drive up and down the valley wine tasting and seeing the sights.
From there I'd cut over towards Petaluma where you can pick up hwy 1 to head north along the coast. I think its even nicer than south of San Francisco and less traffic, if that's possible this time of year. lol
Just know that every where in cali during the summer is crazy busy with most of the parks being "loved to death" so just relax and go with the flow, you'll get there eventually.
And this doesn't look so good to you, you can always go the other way and head over to Death Valley. Pretty amazing things to do and see, but it will be hot!! Go to the lowest point in the US then head north to Scotty's Castile and take the tour.
Happy travels!
