I've had really good expirences with a local chain called "The Guest House". The Renton location is the one closest to seattle for about $80 a night. I've never actually stayed at this location.
http://www.guesthouseintl.com/index.cfm
The Hampton Inn, which is my perfered hotel when i travel, has a location about 10 min south of the stadium for $99 a night.
http://hamptoninn.hilton.com/en/hp/...ionid=XO5KRFNNLCTJ0CSGBJBM22Q?ctyhocn=SEASOHX
Thats where i would be staying had i not had to splurg on the wife to get her to go. If for some reason i can't enough ticket for all my family, i'll probably stay their overnight.