I just thought of another event that will take place near Kirkland on May 12th. They have a car show every Saturday morning with lots of exotics like Lambos and Ferraris and all other nice cars. We showed up with 8 or 10 Vipers one time and it was fun. You can check out the website for information about the event at :
http://www.exoticsatredmondtowncenter.com/ . There are some photos on the Washington website showing one of the shows.
Most of the Viper club members are in the Bellevue area, so perhaps one of them will jump on the forum with some ideas. I am in Bremerton, which is about an hour and a half away, but you are welcome to come and visit on one of the days. I am one of the only Viper owners over here, but I have a garage with lots of Viper stuff and you can do your pre-track mechanical checks here if you decide to run on the Shelton track. I am retired, so I am usually around during the day. You are welcome to call me at 360 377-7220.