Like you, I noted that the road game would be taking place earlier in the season when you stand a better chance of avoiding inclement weather. Problem though, is that my daughter will be in the midst of her high school volleyball season and we've yet to receive an official schedule yet. Judging from last year, there's a 50/50 chance that she could have a tournament that weekend. As a result, I've made hotel reservations in Bellevue for the weekend, but will wait to purchase the airline and game tix.
If we're able to go, we'll likely try to secure tix for seats under the covered parts of the stadium. Looks as though that will run approx. $200 apiece. Hope the volleyball schedule breaks our way. I've never been to Seattle before and think we can get a decent taste of it in a day and a half.