There is ample parking at the venue and right across the street at Ober Park park & ride.
Cocktail attire, whatever that looks like for you. The venue is outdoors in a grassy area.
There are two ferries to Vashon. One leaves from Point Defiance, Tacoma and the other leaves from Fauntleroy, Seattle. They both depart about every 50 minutes, and the ride is an easy 20-25 minutes. You are able to walk on or take your car on. Once on the island, the venue is about a 10-minute drive from the Vashon Island ferry terminal and about a 20-minute drive from the Tahlequah Ferry terminal. The ferries can get busy in the summer, so plan ahead for longer waits.
There may be a few but try to plan ahead if using Uber. Since there aren't many drivers on island, the wait time may be longer. We have heard that the Vashon Taxi is another option: (206) 434-1121 https://vashontaxi.wordpress.com/ Or Jonathan at Island Uber at 206-571-6333