Nathan Natas is correct. The Washington state ferries do run all year barring breakdowns. Even then, since commuters rely on them they bring another one online within a short time (maybe 2 hours or less). One thing, it is pretty cool crossing the Puget Sound in a snow storm. Another note: make sure you have chains and/or 4-wheel drive. Getting up the hill (or down) at Mukilteo can take over an hour in the snow (it is normally about 3 min.) And, (I feel a flame coming) Washintonians can't drive in the rain or in the snow (sweeping generality).
There are a lot of Reservations in the Seattle area. As things go, not overly interesting unless you are into casinos, tobacco or fireworks. But the scenery can be very nice. For example the Swinomish reservation and the Marysville reservation. Many, not all, of the long-time residents of Washington take a pretty dim view of Indian people.
I lived there some when I was a kid. One of my friends, a woman older than me at the time, made the mistake of saying something to one of her caucasian "friends" once about being of indigenous ancestry. The (other) woman was horrified. "But, I thought you were Mexican. So that's alright!" The old witch (spelled with a 'B'.)
When you get to the bridge that spans the slough (bayou) that separates the island (I think it is Fidalgo Island, not Lopez Island like I said yesterday) from the mainland look to the left and you will see the Casino. You have to cross the median (it is a 4-lane road but legal to cross). The tobacco shop is next door to the casino. If you don't see it, stop at any restaurant along the way or store and they will tell you how to get there.
Have fun! And smoke one for me.