In May, the Oregon and Washington coasts can be cool and misty, but still pretty interesting. As "stickdog" says, it's quieter before schools are out for the summer. That's also the case after they've gone back in the fall. We've cut way back on trips between late June and Labor Day. If we go during that time-frame, we leave home Sunday and head home again Friday, leaving weekend space for those who have to work 5 days a week.
BTW, out west, particularly Washington and Oregon there are hundreds of State Parks which are all excellent places to stay.