Will old Apple Watch models work with AirPower?
Yes!


  AirPower works with the new series 3 Apple Watch, as well as the Apple
  Watch Series 2, the original Apple Watch, the Appel Watch Edition,
  Apple Watch Hermes, and the Apple Watch Nike+.


https://www.macworld.com/article/3224389/mobile-accessories/apple-airpower-features-specs-price-faq.html