ascanio1,
While I have tried to digest most of your posts and I have commend your careful planning. Your effort to collect the needed information is also much more than I usually expect. Good Man.
There is, however, an issue that you should also study carefully. This has been an issue with visiting family from Europe. The US is a big place.
Yellowstone is an amazing place, but it is about 1000miles (1600Km) from LAX. That may be a stopper right there. Even with two very capable drivers, that is a long way to go. I strongly suggest that you use all the planning capability you can find to determine your schedule. Yellowstone is about a 5 day park by itself.
The Grand Canyon and Yosemite part of the plan is nearly possible. But remember to include that you will lose a day at each end for the acquire and return of the vehicle.
I wish you luck that is hours of driving without problems and memories that make it all worth the effort.
Matt
