Local big club is Cascade Bicycle Club.
Cascade Bicycle Club: Page Not Found | 404 Error (link does not work, so from
Cascade Bicycle Club: Seattle, Washington; STP, Seattle to Portland Bike Ride, Bike To Work, Bike Expo, Ride Around Washington, RAW, bicycle advocacy, bicycle education pick Events and Rides, then Daily Rides, then Calendar). Looking at that weekend, as avisitor I might be tempted by the Ballard ride on Sunday - just for the education and being shown around a specific neighborhood. Beware that the standard of riding can get poor on the slow rides. Bike hire from Greggs of Greenlake
Greggs Cycles: Page Not Found Pike Place Market (see your guide book) is entertaining for a visit, some nice restaurants around there. I remember a mexican one with a balcony overlooking the market.
A non fancy place is Ivars Fish Bar
Ivar's Seafood - Seattle's Best Seafood and Chowder go to the lakeside one in Wallingford
Ivar's Seafood - Seattle's Best Seafood and Chowder the clam chowder is a must and you can get Salmon sampler plates with 3 different types of salmon - an education for those brought up on John West. Use the restaurant not the Ivars outlet outside or those in the shopping malls.
Oddly convenient
this is very close to Recycled Cycles
Recycled Cycles | Seattle's Used Bike Shop | which is very busy at weekends. This is not a flashy place. They sell new practical bikes and second hand bikes and lots of secondhand bits.
Pioneer Square - the old original heart of Seattle might be worth a visit
Pioneer Square SeattleOn a short visit with only a few spare hours (before I lived there) I took a bus tour
Seattle sightseeing and Pacific Northwest vacation options which was ok for showing neighborhoods and viewpoints you would not necessarily find as a tourist.
Touristy bits you will have covered in the guide book. Like most places I've lived I seldom went downtown and of course my views have been jaundiced by living there.