Stay at the Lake Pleasant RV Park in Bothell, WA. This is a good base camp for Seattle. Go to nearby McMenamins Anderson School beer pub/restaurant...great/fun place. Stayed there in July.
Some places to visit in Seattle:
Starbuck's 1st coffee shop (Pikes PL Mkt) & new Reserve Roastery
Lake Union (Sleepless in Seattle)
Larry & Sue
2005 Georgie Boy Pursuit 3180DS, 31'5" Class A, 18K GVWR, 208", F53/V10, CHF, TST 507, FMCA, GoodSam