Oasis Bob, you didn't say that the kids are in school but I bet they are and you may even be working and, therefore, probably out on week ends. If this is true, reservations will be mandatory in many areas of the NW. It may be a slight inconvenience but it shouldn't be a problem.
If you're going week days it maybe necessary for really popular areas.
We make reservation once or twice at a new(to us) campground just to get a feel for occupancy. If after a couple of visits we see lots of vacancies, we don't make reservations.