I'll add Whidby Island, Annacortres, the North Cascades Loop US 20 over the Cascades to Winthrop, a summer cow town resort area, down to Wanatchee and US 2 to Leavenworth and over Stevens Pass back to Seattle. There are several good campgrounds: Fidalago Bay at Annacortes, Riverbend south of Winthrop in Twist, Wenatchee River County Park in Cashmere, and Icicle River in Leavenworth.