If I were you I would pass on campground memberships. There are so many options for camping why restrict yourselves to private membership campgrounds. We much prefer public (state parks, national parks, national forests, Corps of Engineer, and sometimes county/city park campgrounds). They are more natural and generally lower costs. The national pass would be a good idea. Many states do sell annual passes but may not pay, depending on how many parks in that state you would visit and whether or not entrance is included in the price of camping.