maybe check out http://www.pacificstarwinery.com/pacstar/index.jsp

It is just north of Ft Bragg so really convenient to visit while you are staying in Mendocino. Really a beautiful setting for a winery

R5 is right on about Queenies!

My two cents is to take 101 then 128 over to the coast. 128 is a beautiful road and one loaded with wineries. The hwy on the N Coast is one that requires an enormous amount of time for safety's sake.

Since you will be spending a night in Guerneville,I'd recommend the same route back.

You will get some good time on the north coast and a chance to enjoy its splendor. Point Reyes is a place one should languish in. It's a national seashore so there are many places to walk within its borders. I'd say save it for another visit.

Goat Rock Beach is a good choice. The sea lions pup there although I think "pup season" is over.

Have a great trip!