Oh gosh - camping with kids and you are the only adult is H E double hockey sticks!
I did that a couple years ago with my two youngest and one of their friends. Due to a mix-up, we had to hike to our spot rather than have one of those sites where you pitch the tent right by the car. I went back to make sure the lil one was okay. When we caught up with my older kid and her friend, I saw that her idiot friend was wheeling a suitcase over the rocky terrain!
We had stopped at Casa de Fruta (a touristy rest stop) where I got some wine, having this fantasy that I would have a glass under the stars while the kids were all snug in their bags inside the tent. That of course didn't happen, as every noise became some horrible night creature.
On our last day, we went to Santa Cruz Boardwalk. But first, after leaving our campsite, I took them to the beach....which turned out to be an "unofficial" nude beach - something only the locals know (maybe this should go in the awkward thread).
Anyway - once we got to the boardwalk, we had a great time.
last year's trip camping near Crescent City was a blast though...we didn't take the friend....maybe it was all HER fault...