Capitol Hill is a few hours tops. Urban, dirty, street people, urban campers ie homeless, some great food and some pretty neighborhoods with big old Seattle mansions but nothing I would go out of my way to plan for a day. Molly Moon is a local chain and has a Queen Anne Hill shop (Queen Anne is a lovely neighborhood but also getting more crowded and more homeless) and Wallingford shop too.
Underground Tours of Pioneer Square are interesting and a staple for field trips so good for kids. Space Needle is being renovated so not sure observation deck is open, Seattle Center has activities and food and you can take the monorail from downtown right to it and kids like the monorail, Pike Place Market is interesting and they have ghost tours that can be good, University of Washington has a nice campus
and light rail to it if your teen is thinking of college, ferry to Bainbridge is nice day trip. Great bakeries and food and shops when walk off the ferry. If you do rent a car, can drive on and explore. Entire section of commuters do ferries every morning to the city core. South Lake Union home
Of amazon and more. Museum of Modern History right on the bank of Lake Union and good food in SLU. Seattle Art Museum downtown , right across from Pike Place Market. But if I was in LA, I would visit Seattle in a different time of year. Good luck.
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