If you want to see much of our fair city, you'll have to do it Fri morning, or else come or stay a day early/late. Fri evening class runs until about 9, and Sat/Sun are full. Well worth the trip for the class alone.
Downtown Seattle has an aquarium on Pier 70, the EMP (Experience Music Project, a music museum funded by Paul Allen), Pike Place Market, Pioneer Square and the tour of underground Seattle. You can "ride the duck" for a motorized tour.