
I want to organize a camping weekend for a large group of friends. Let's say 30 vehicles, though the group may be ±10 vehicles. Some, like me, will be towing campers, most will probably be tent camping. I'd like to do this campout in late July or early August. I'd like it to be somewhere that will be warm and also has lake or river swimming access. I'd like the location to be within 150 miles of San Francisco, but am open to suggestions that are further afield.
Do you know of any place that fulfills all or most of my parameters? If so, please speak up!

I found a place near Guerneville that seemed perfect, Schoolhouse Canyon Campground, but they are not at all amenable to groups.

Regards-HW