I have a 14 year old who will be in town on a Saturday in Octovber for his birthday. Anything fun to do there?
It's been a while since I've been up to eastern Washington state, but I recall that if the boy is from the city, a trip to pick apples on a farm might be nice. I don't recall Yakima being noted for its urban amenities, so experiencing outdoor activities is probably the best bet assuming the weather cooperates. Good luck.
As far as I know there's not much else to do there, although you can probably scare up some pretty good Mexican food.
Of course you'll have to do wineries without the 14 year old.
If you're coming from the north on Hwy 90, you could make reservations at Chimposium, run by the communications institute in Ellensburg that has taught 3 chimpanzees to speak in American Sign Language. That might be something different that a teenager would be interested in. Here's a link with an email address:
There is the Gorge Amphitheatre nearby in George Washington. Maybe a concert will be playing on that day. The schedule isn't out yet. You can camp overnight up there too. Or just take him camping somewhere around the river or rent a cabin somewhere. Any kid would like that.