First, you need to decide where you want to stay. If it's near Redmond look for prices to actually drop a little at some hotels as they are mostly geared towards the local business traffic Mon-Fri. Remember you're in a section of town where rents start around $2500/mo, it's Microsoft central. If you want to stay in Downtown just look around. Still, driving back and forth to see your family is going to be a pain. Seattle has traffic you have to see to believe. And again, hotels are not cheap, because in some cases they are being filled with extended stay customers who can't find a place to live.
Downtown I like the Hotel Sorrento, the Sheraton, and the Arctic Club. The Marriott Courtyard is good, and the W over by Queen Anne is nice. The Element in Redmond is good, and the Hampton Inn at Marymount is too.
Don't stay near the airport, it may be cheaper but traffic will kill you.
Not to miss? Go see Paul Allen's collection of WWII tanks and airplanes. They even fly them some weekends.
https://flyingheritage.org/
If you like wooden boats go to the Wooden Boat Museum.
If you want to check out antiques Pacific Galleries is the place. (Occasionally you can find a nice knife or two.)
For eclectic neighborhoods, try Fremont on a Saturday morning. Just park near the Lenin statue, or a block over at Google HQ, and walk around. And alternate to that would be Edmonds. Both have good Saturday markets.
You want to see bums, Pioneer Square downtown, or just cruise under the West Seattle viaduct.
For your recreational weed, just follow the billboards.
For seafood Anthony's is the best local chain. Ivar's for clams and chowder. Salty's at Alki has a great view of the city at sundown as well as good food.
If you like glass art Chihuly's is the foremost place in the USA. Really amazing.
If you like old airplanes the Boeing Museum of Flight.
If you like old cars go down to Tacoma and visit the LeMay Car Collection.
If you want to have an incredible Sunday Brunch go to Palisade.
You want a really nice, intimate, dinner in a bistro nobody's heard of try De La Terre in Steilacoom.
You want to see the country and a place where they filmed the TV series Northern Exposure drive up I80 to Roslyn and Cle Elum.
You want to visit a world class winery go to Chateau St Micheal in Woodinville.
If you need/want outdoor gear REI is local (the Seattle store is best) and Filson, Outdoor Research, Ex Officio, and Carhartts are all local and have outlets. Nordstrom Rack is a place to keep the wife away from.
If you have more specific requests I can probably make better recommendations.
Have fun!