Plot out your route on Google Maps, and make note of the drive times between points. Add 20% to those, and this will tell you just how long it's going to take you to get from point A to point B with no sightseeing, just basic stops (fuel, food on the fly, leg stretching, and bathroom). Add in your off-the-road sleep and dead times and sightseeing stops and see how the math comes up. I can foresee a very cranky 7 year old if you try to pack too much stuff in.