At a minimum, a DUI conviction in Washington State will require a day in jail, court fines, and ignition interlock on your vehicle for one year, SR 22 insurance for three years, trouble entering Canada, and a criminal conviction that remains on your record for life. Getting a DUI charge reduced to Reckless Driving or Negligent Driving will help avoid the jail sentence, reduce or eliminate the need for an ignition interlock, and provide an opportunity to vacate the conviction off your record after a period of time.
Prosecutors will not reduce your charge just because you are a nice person and the charge is your first criminal offense. There needs to be a legitimate, evidentiary issue with the case. In other words, if you push the case to motions hearing or trial, you have a legitimate chance of the judge or jury ruling in your favor.
Read about the initial stop and arrest for a DUI offense.