This is a little late as it started today but anyone looking for something aviation related near Yakima should check out the Great Prosser Balloon Rally this weekend. You can fly in and camp on the field (S40). Restrooms and showers on the field as well as tie downs. (you may need to bring your own ropes though)

I drove down last year for the morning launch one day and the Saturday night glow. Might be flying down Saturday night this year for the night glow. If I do I'm going to camp out and stay for the launch on Sunday morning.

http://www.prosserballoonrally.org/