For your family it would cut the camping at all national parks, some state parks and most corps of engineer parks to half price. Since your dh is a vet and disabled you should be able to get the pass for your entire family at a fairly cheap price. Besides the camping it makes going into national parks free for however many are in your vehicle up to a certain price and kids under a certain age are free anyway. So your whole family should be covered.
We generally camp stay at corps of engineer campgrounds while we are traveling. If you find all of the above are full then check for discounts such as AAA, Veterans/Military, your auto insurance company, and for folks on disability at all the commercial campgrounds. Also check to see if they have stay so many days and so many are free. Many campgrounds have that unadvertised special.
Then there are always the campground special’s Good Sam’s—the camping company not the big box store, Sam’s Club, Cosco probably has discounts too, KOA, Woodalls, Campersworld (maybe camping world I forget which), Coast to Coast, Campgrounds of America. These all generally charge a fee to purchase the card initially, but then you get so much off per night and so many nights free after so many. I’d comparison shop.