The best venue is outside in the fresh air down by the water. Washington fans love mingling with visiting fans and chances are they will invite you on their boat and even give you a spin around the island before or after the game. Right next to the water is a place called 'The Zone' and it's loaded with big screen TV's, tables & chairs, beer booths, coffee booths, food court, etc..
Do you want to be inside a hot musty old building before kickoff or would you rather be getting some fresh air and mingling with Washington fans while pounding beers? If I was spending that kind of time and money to fly to Seattle I'd want to get the most out of my trip. Husky Stadium is like no other college football setting in the world.
I get indoor tailgate is sort of lame. BUT- As someone that has been to a lot of these things at many venues there is something to be said for climate control on really hot or cold days. The number of times being under a big tent lined up with really nice weather are depressingly few.
I've only traveled to those games by boat, but I've heard they expanded the parking since the stadium renovation in '13.
