Calaveras Big Trees State Park is up that way....I haven't camped there, though, in a month of Sundays.
If you want the shore, and close to home, you could try Doran Beach or Stillwater Cove (Both Sonoma County Parks. Neither has hookup and Doran is pretty popular. I think Lake Solano (Solano County Park) is open for camping now; it's one of my favorite close to home spots. There are some sites with electric.
My grands have the week before Easter as spring break, but some schools may have the week after, which sounds like your target. I hope you find a great spot!
--Time and trouble will tame an advanced young woman, but an advanced older woman is uncontrollable by any earthly force. --Dorothy Sayers