It is possible to fly to Yakima, but you'll most likely to have to fly to Sea-Tac and then take the 20 minute flight over to Yakima. Those flights only happen maybe 2-3 times a day right now.
It may be easier to fly to Seattle or Portland and then rent a car for the weekend to drive in, that would also open up your transportation options.
Yakima is about a 3 hour drive from both Portland and Seattle.
From Portland, you can drive east along the Columbia River on I-84 and cross the river past The Dalles to drive north up Satus Pass and dip into the Yakima Valley.
From Seattle, you can drive east through Snoqualmie Pass on I-90 and then drive south once you pass Ellensburg down into the Yakima Valley.
Information about hotel blocks will be available soon.
https://www.hilton.com/en/hotels/ykmnhru-tru-yakima-airport/
https://www.hilton.com/en/hotels/ykmwaht-home2-suites-yakima-airport/