Where in WA do you live? I grew up in WA myself, but have lived on the east coast for the past five years, so I make that long trek a lot - usually with my DS5 and DD3 in tow. It's never easy, but it's also never as hard as I think it's going to be.
Most of the pps gave you great lists. I always bring the sippy cups with straws in them and make my kids take little sips on the way up and the way down. I just ask them, "Are your ears starting to feel funny?" And if they answer yes, more sips. The sucking motion clears their ears better than food or even lollipops. Plus I like to avoid giving them sugar when we travel.

As far as snacks go, I like to bring "carbish" type foods that are low in sugar. Bagels, crackers, bananas - things that I know won't upset their stomach. We also avoid dairy and even juice - they have "come up" before on flights, and I hope to never see them again.

One favorite treat for my kids is the Ritz Bitz crackers with the peanut butter middle.
I
highly recommend investing in a portable DVD player if you can. I agree with a pp who said they don't like to plop their kids in front of the telly, but when we're traveling we always say we go from "No" parents to "Yes" parents. That's the whole point of vacation, right?

I always bring DVDs that they like, and they each get a new one for each trip. I wrap it up in wrapping paper and they get to open it once we get in the air. They really look forward to seeing what their new DVDs are.
Another staple for me when traveling with my kids are the DK sticker books. You can get them in the "games and activities" section of the kids' section at Barnes and Noble. (I've seen them other places, but I know they can be found here and they have a good selection.) They have Disney and Nickelodeon themes, and everything from bugs to ballerinas and everything in between. They have sheets of stickers in the middle of the book, and then pages with the outlines of the stickers. My kids love to see if they can match the stickers to their outlines, or vice versa. And it's great for takeoff and landing because you don't need the pull down tray to do it.
Guess those are our big ones. Good luck - you'll do great!