On a trip like this, time driving is never wasted. Nobody drives entirely across the country and back unless the drive IS the "destination". That's why I brought it up early on in this thread.
Now, *if* what OP is really concerned about is Point A and Point B and none of what is in between, then yes the drive makes little sense. But, it sounded like OP has more than one destination in mind. And doing multiple stops in a single trip via plane is at least as much of a pain as it is by car, not to mention WAY more expensive. What OP has to decide is if there's enough of those attractions between A & B to make the drive interesting, and also if they are willing to commit the time needed to do it right.