you need at least 2 days, preferably 3 at the olympics np. Also, if you have never been to seattle before, it is worth a visit, there are some museums and the needle tower in the downtown area. imo, you should spend at least a day or 1.5 days in seattle. lastly, if you are going to visit oregon, you might as well go visit the canon beach, it is just south of olympics np.
多谢