I know of a few friends who always stay at Lincoln Rock State Park:
http://www.parks.wa.gov/parks/?selec...Lincoln%20Rock, so that might be a viable option for you. Also, check the state park and campground site for places that might be East of Wenatchee, on your way into town.
http://www.parks.wa.gov/default.aspx...v/parkpage.asp

Have fun!
Mary