It's been awhile since we've been to the Santa Cruz area but we remember that the KOA in the area was nice.
They have the Kamping Kabins and I think they have the Kamping Kabins with private bathrooms if desired. I think they also have a couple of those large outdoor kitchens that your group could gather at and cook or eat at, and they sponsor ice cream socials and bingo in the evenings.
The week of July 4th they usually have a parade and extra activities..
Maybe someone else has been there lately and can tell you more about it.
Your whole family could be together whether RVing, camping in a tent or reserving a Kamping Kabin. I do believe the rates are "up there"... but most everything in that area is.
Here's a link to the Santa Cruz/Monterey area KOA:
Good luck to you.