I was in the Shelter Cove/ Mattole area last week. Drove the Kings Peak road from Shelter cove to Wilder Ridge. Road was in good shape, no need for four wheel drive, although unless you want to drive dirt the Ettersburg road would probably be easier and quicker. The Tolkan campground was nice, but again unless you want to drive dirt I don't think I would go out of my way to stay there. I spent one night at Wailaki which was nice (on the creek. Checked out Honeydew, which was also nice. The County Park campground was big and expensive. Speaking of expensive I was a but surprised at the state park/national park prices at the campgrounds, $30! Years ago I stayed at Prairie Creek, and it's great (especially when you do the Fern Canyon loop hike), but again $30!
Walking Black Sands beach was awesome, and Mattole campground/beach is a can't be missed! Quite windy though, the walk to the lighthouse is wonderful! Seeing where the river enters the ocean at low tide is beautiful!
Make sure you take the road from Ferndale! Although, I was pretty amazed at the steepness and constant up and down.
The hike to the Boy Scout Tree in Jedediah Smith is nice and the drive is awesome!
As a side note, also went to Lava Beds national monument. The lava tubes were amazing.