The more I research Alki, the more it strikes me as a sort of California beach town along the lines of a hybrid Venice Beach and Carpinteria. Surf shops and burger joints, along with more upscale dining, line the beach as does a 2.5 mile (5 mile round trip) bike path. While the beach itself may not be the kind of white sand and waves Californian's expect, bonfires are still permitted--which makes the idea of watching the sunset over Seattle pretty damn appealing.
Within walking distance from the ferry dock (roughly 2 miles) there is also the 53 acre Schmitz Preserve Park which has the largest old growth forest in Seattle.
So Alki now tops the list of places to check out. In part, because it can be accessed so easily via the King County water taxi from Pier 50. (Nothing I love more than a water taxi or a ferry.) The water taxi runs year round, and at this time of year, leaves every 30 minutes. And at $4.75 each way, the 12 minute crossing is a bargain.