Lots to do in Seattle, not sure what your interest are but a few things .....
Museum of Flight
The
Hiram M. Chittenden Locks where the fresh water system meets the Puget Sound is interesting, there is the fish ladder and the a salmon run may be occurring depending on the time you visit in September. The gardens and sounds are well maintained and there is always marine traffic, large and small, passing through the locks.
Seattle Center and the
Space Needle always have a number of events happing, The
EMP museum is always a fun spot and is located adjacent to Seattle Center. Also the
Pacific Science Center is also located adjacent to the Seattle Center and always have interesting exhibits and something good playing at their IMAX theater.
If you are in town on Labor Day Weekend there is also the music festival
Bumbershoot that runs September 5, 6, & 7.
A dinner reservation around sunset at
Salty's restaurant along Alki Beach in West Seattle is a great way to watch the Seattle Skyline light, a fantastic view.
Just hanging out downtown with the
Pike Street Market, the
Aquarium, the many waterfront shops, the
Seattle Art Museum, and downtown stores.
There is also the chance to see a Mariners baseball game if they are in town. Good seats are always available.
There is also
Volunteer Park with the
Conservatory and the
Asian Art Museum. Right next to Volunteer Park is the
Lake View Cemetery considered Seattle's Pioneer Cemetery where many of Seattle's founding families are buried. You will also find the grave site of Bruce Lee and his son Brandon Lee on the grounds.
There are gardens and urban trails as well, a lot to find in Seattle and I am sure you will find something fun and interesting to fill your visit.
Enjoy and happy to answer any questions you may have. Feel free to send along a PM or email.