@Kevin1 I would suggest campgrounds on any of the islands in Channel islands National Park. I checked the page for Santa Rosa Island campground and they are not yet taking reservations for the 4th.
The island is really different from the mainland and most visitors have an enjoyable experience. The drawbacks are that getting to Santa Rosa Island is not cheap (concessionaire boat ride) and you are isolated (may be a positive- depends). Cell service is marginal. You must be self-sufficient - no stores on the island. If you didn't bring it, it is not available.
There is also a campground on Anacapa Island - much smaller island, maybe a bit too small for along weekend. There is a campground on San Miguel Island. I am not sure about its status. If you enjoy wild places, San Miguel is hard to beat.
I didn'tmentionit, but Scorpion Ranch and campground is closed for now, due to construction of a new pier. That is the largest, most accessible, and most popular CG in the park...