Here are a few of the benefits of car camping in your National or State Park system:  

• Many parks have facilities with hot showers and electrical outlets.  This may just be enough to coax a reluctant family member along.  Once they get a taste of the outdoors, who knows what can happen after that.
• Many of these manicured campsites are right next to where you park the car.  You can bring (and store) large bulky and heavy items from home instead of having to buy expensive, light and compact items for camping.  For example, you don't need sleeping bags if you already have old blankets.
• Chances are, a friend or relative can lend your family what you need.
• Many parks have a fire-ring, grill or picnic table nearby (or even in your individual campsite).
• Some parks have useful services and facilities like, dumpsters, visitor centers, drinking water faucets, pavilions, etc.
• There are close-by natural recreation opportunities such as a trail system, a water source for swimming, boating and fishing, and many other possibilities.
• Many things that can be a joy-kill to families with kids (like excessive noise and alcohol) are prohibited and enforced.  In my experience, park rangers patrol constantly, even at night. Statistically, there is only a fraction of crime as compared to crimes reported in "nice neighborhoods".
• Your kids may have opportunities to participate in educational, fun, nature activities offered at parks.  Meeting other folks that love the outdoors can't be bad either.
• State and National parks do an excellent job on their websites.  You can download maps, get good information, view the "calendar of events", pick your campsite and make reservations -- all online.
• You can usually get a free map of the park near the park entrance. 
• Park rangers and employees began as nature freaks too!  That's why they work there.  Many park employees have degrees in biology, forestry, environmental sciences, etc. and appreciate your interest.  Most will go out of their way to help you want to come back. 
• Any fees or money you spend will go back into nature through managing the park, conservation, education, etc.  Not into the commercial tourist industry.

     There are some down sides to car camping in government or private parks.  Quite frankly, the negatives are not worth mentioning.  The benefits outweigh any complaints.  Go, get your family and go!  Go now... quickly!

Also -- Places like KOA are not a bad choice either -- if near natural areas or State Parks.  Just remember, you are trying to avoid civilization and the constant bombardment of advertisers.