One more thought about Death Valley. It is one of my all-time favorite places in the USA. You can get a nice overview from driving through -- but all of the places you mentioned requires that one get out of the car and spend a few minutes walking around. 55-c degrees is an interesting novelty -- the first time -- but interest will wane if you try and do it more than once or twice a day. (Don't forget to tell everyone -- AVOID TOUCHING THE OUTSIDE OF THE CAR DOOR)

Anyway, I am sure that this will be a grand adventure.

An alternative to the southern route along the coast -- drive over Sonora Pass. Even in August there will be waterfalls all over the place. And then south on US 395 and over to Death Valley (if you really must drive that much.)

Mark