If you're going thru the north part of CA (which I think is where the big trees are) then you'll probably miss Yosemite (it's pretty far east- almost Nevada) and Tahoe (border of Nevada and CA). I'd take the coastal route- maybe hit Sacramento (state capital) and head down to SF. Monterey is BEAUTIFUL and I'd skip SF in favor of Monterey. You can go down the coast to LA and hit Half Moon Bay (great brewery), SF, Santa Cruz, Monterey, Carmel, Big Sur, Cambria (see Hurst Castle), Santa Barbara, San Clemente (I think it's N. of L.A. for breakfast), then LA. Heck, you could spend a full 2 weeks doing THAT drive alone! DH and I have done the south from Monterey (used to live there) and then the north from SF so we've driven the whole coast. It's fun!

Whatever you decide to do you'll have a GREAT trip.