Sausalito is a madhouse on weekends now, but it does have a lot of places to eat and the advantage of frequent ferries. Lots of people rent bikes in the city and ferry over to Sausalito. Only problem is the ferry line going back to the city after dinner.
Tiburon is more charming; there's also a cool little museum that shows you how the town was once a big railyard (they ferried railroads over from SF). Now it's among the priciest real estate in the country.
Still is and still hugely popular with the tourists. I believe they sell out weeks in advance now; at least during the summer.
Also in Marin, if you want to go to Muir Woods, you need to make a reservation -- no joke -- and also sells out weeks in advance. Used to be first come, first served on parking but someone over-thought the problem so now they turn locals away from empty parking lots at 5 pm on a Wednesday because they 'don't have a reservation'.
Of course, you have a whole mountain full of redwoods with all kinds of trails of varying degrees of difficulty, so really nothing that special about that one little section.
Come to Mill Valley for breakfast and hike the Dipsea trail out to Stinson Beach!