If you take the River Road route to Timber Cove Inn you'll meander through Guerneville with LOTS of great stops to make in town but if you have a little time and your hiking shoes (I wore my flippy floppys so it's not serious hiking) "Armstrong Redwoods" is a must-do. It's maybe 10 minutes west of Guerneville but worlds away from civilization. Redwoods are spectacular. The trails are beautifully marked and so quiet, people whisper hello as they pass**. This is not the biggest Redwood Reserve (805 acres) but my-oh-my it is a sight to behold. You will see giant redwoods with "burls" growing on their sides. A bullfrog pond. The oldest tree, tallest tree and biggest tree. (Also the deadest tree but that isn't in the brochure). Magical place. Easy to get to.
** The REASON dear friends that it is so quiet is that this particular grove doesn't allow much sunshine to reach the forest floor and because of this, only a few plants and trees can thrive here. Consequently, a limited bird and animal population will visit for a meal or some rest in the cool shade. You will need to use your inside voice in this special place.