Easter is always on Sunday (duh), so it's either never or always a holiday, depending on your outlook and what the word "holiday" means to you.
Neither Good Friday nor Easter Monday are public holidays in Washington State. Some businesses might, I suppose, close for them, but not many.
They're not generally school holidays either, but almost all schools have a one-week spring break around that time. Different private schools have different breaks, and the public schools in different school districts may as well. At one time in history, the breaks used to be more oriented around Easter (they were even called "Easter break"), but now they're pretty much unmoored from the ecclesiastical calendar, except for Catholic schools.
If you're worrying about ski areas being crowded, don't. Almost nobody skis in April.