I have KOA, Passport America, AAA, and the America the Beautiful senior pass. I've used them all extensively.
1. KOA I'd recommend shopping for the back in water electric site which is usually cheaper than the full hookup site. Skip the keep on adding stuff. I generally enjoy their parks..
2. Passport America is great. There are some nice campgrounds on the list and there are others which are good for overnight. I used it four times in the last couple of weeks. Just look over campground list in advance with the "notes" and see if anything is useful to the tune of more than $50 per year.
3. Best of all is the US geezer pass.