I would suggest Grandview campground in the white mountains near ancient Bristlecone pine forest. 8500' I have been many years ago, and I believe it is still one of the better dark sky locations in the western US. I am 90% sure it is trailer friendly, I am planning on taking my 22' in the next year or so.
I would also suggest Thorndike or Mahogany Flat campground in the Panamint mountains, but I am not sure if you can get your trailer up there. Really most anyplace in DV. When I live closer I used to take weekend trips, often leaving in the evening. I have been known to just pull off the Trona Wildrose road in the middle of Panamint valley and just look up!
Our own local Mt. Pinos west of Frazier park is one of the better dark sky locations near SoCal.
I have also read good things about Bridgeport.
It is a bit frustrating for me, I love the night sky, my family couldn't care less. My oldest is beginning to show some signs of interest so I am going to try to encourage it. Where I grew up in Hesperia we had respectable dark at night, now I live in SCV not so much. I miss it.
