G'day!
Passport America is a half price camping club that always pays for itself with us. They do have restrictions on when you can get the discount, but we just read the restrictions before we decide to stay there. www.passportamerica.com
You will get mixed comments about this but we also like KOA (Kampgrounds of America). They are expensive but usually are fairly nice and have lots for kids to do. They have a value card you can sign up for and get 10% off their sites. You also earn points and can convert the points to coupons for discounts on future stops. If you don't want a fancy site, many KOA's have back in water electric sites that are cheaper than full hookups with cable, etc. www.koa.com for more info.
Another campground organization is Yogi Bear's Jellystone www.campjellystone.com
They are also expensive but have lots for kids to do. Not sure if they have a discount program.
you can find national campgrounds on www.recreation.gov
Free sites we use www.woodalls.com to locate campgrounds and we always check www.rvparkreviews.com before we stop there.
We use www.mapquest to map to the next location and add stops along the way.
We have a Class A and use Coach Net for our roadside assistance. Good Sam also had roadside assistance. I would find one that specializes in RV travel.
Enjoy your stay!