Various locations around town
They'll probably be a little horrified when you first suggest it -- you want me to put WHAT on a hot dog?! -- but once they try the admittedly strange combination of grilled onions and cream cheese on a lightly toasted bun, they'll understand why, for the last 20 years, the Seattle Dog has been a mainstay at street food vendors across the city.
Play vintage video games that you can still win
Home to Nintendo, Microsoft, Valve, and a slew of other game developers, Seattle has always been a gaming town, so it shouldn't be surprising to find a handful of places still offering the kind of games your guests probably grew-up playing, including the no-frills Add-a-Ball arcade in a Fremont basement, and the Seattle Pinball Museum, where you'll find dozens of old school machines.
Get coffee at the Starbucks Reserve Roastery
Sure, you could take them to the "original" Starbucks in Pike Place Market (FYI, the first location actually opened down the street in 1971 but moved to the current address five years later), but once you get past the crowds there isn't much there. Instead, hit the Reserve Roastery and Tasting Room in Pike/Pine, where you get an intimate view of both the roasting and the brewing process, and you can try things like whiskey barrel-aged cold brew.
Helmed by one Seattle's best chefs, Renee Erickson, General Porpoise Doughnuts is quickly becoming a Seattle institution thanks to classic baked goods made with fresh local ingredients. There are currently two public locations (and an Amazon employee-only location), but a third will be opening soon, making it even easier to get your hands on these tasty treats.
Let's face it, you don't go to a Mariners game for the baseball -- the team's current playoff drought is longer than any other team in sports -- but you should go for that feeling you get sitting in the bleachers on a sunny day, listening to the crack of the bat, and eating a hot dog (or because this is Seattle, some sushi, or Din Tai Fung's world-famous dumplings). And the best part? Tickets cost as little as $7.