I'm assuming you're looking for a Wii. Any video game store will carry them. Since the console has been out for awhile, you shouldn't find any issues with availability. If by 'local' you mean close to West Seattle, then there's Target, Gamestop, or Game Crazy. I'm not aware of any locally owned game stores in the area- but maybe someone can step in with more info.
When you go to the store, you'll have to remember to purchase all of the 'ancillary' items to make the system playable. I believe it only comes with one controller, so if there are three kids you'll definitely want to buy at least one more controller, or maybe a third (depending on what game they are playing). The basic console has a variety of cool sports games (bowling, tennis, boxing, etc) but there are some really awesome cooperative games out there that force you to utilize teamwork to be successful (the new Super Mario game comes to mind). At any rate, all of the places I mentioned will be able to tell you what to buy if you let them know the ages of the kids and your price range. Good luck! I'm sure the kids are going to love it... and don't be surprised if the adults end up taking over!