I'd like a camping spot where I can take my two kids (8&10), park the
car, pitch a tent, campfire, a little hiking and maybe fishing, BUT
NOT A CROWDED RV PARK. As close to Rancho Santa Fe as possible

Have you tried Cuyamaca State Park?  The Green Valley campground in
Cuyamaca is very nice.  I recently took my two boys (ages 4 and 6) for
a two-night tent camping trip there and we had a great time.  There
are several fairly private, partially shaded sites within Green
Valley--you might occasionally hear other campers out in the distance
but they'll be out of sight.  For fishing, Lake Cuyamaca is just a
short drive from the campground.

I was amazed at the cleanliness of this campground--especially the
bathrooms and showers.

You might also check out Dixon Lake in Escondido.  Some of the sites
there can be private and many have fantastic views overlooking either
the lake or Escondido.  This campground is not nearly as well
maintained as Green Valley but it is considerably closer to Rancho
Santa Fe.