Not being able to go (conflict on the 15th) but when I first proposed the location, I wasn't talking about Usal Beach. I would not
recommend it for the 2wd sprinters during the Spring. After a storm, the road in can get very muddy, and the last down hill stretch to the beach could be problematic. During dry weather it would not be a problem. The location I was proposing was further north.
Take a look at the Google Map Link below
Wailaki campground is my recommendation for the group meet. It is easy to get to (paved) but relatively remote. Its a BML campground. Here is the description
Tolkan is another good option for a BML mountain campground. Further north is the mouth of the Mattole River CC. Right on the beach. Needle Rock is a picture perfect location but it is a tent/pack-in campground with only one vehicle camp. It is a nice day-use park but you have to pay the high park fee.
There are more opportunities for Boondocking but not for a large group of vehicles. (At least that I know of.)
Let me know if you need further information.
Wish I could go, but can't on that date.