Greetings!

My husband and I, along with our six children ages 1,3,5,9,11,12 will be traveling to visit family in Las Vegas and San Diego next year (2018). This will be our children's first time going west (we live in Florida) and so besides the excitement of meeting a lot of extended family for the first time, we are really wanting them to experience the incredible landscape which is unlike anything they have ever seen. The dates we are planning on are March 27-April 9th, so 13 days. This is the ROUGH itinerary/route I was thinking.

Day 1 - fly into Phoenix around 10 AM and drive straight towards our Sedona hotel, making stops at Montezuma Castle, Red Rock State Park and Chapel of Holy Cross which are all right off the interstate before Sedona. Sleep in Sedona.
Day 2 - Drive to Grand Canyon, first making a stop of Slide Rock State Park, which is on the way. Spend the rest of day at The Grand Canyon and stay overnight
**total drive time so far - about 4 hours

Day 3 - Spend the morning at the GC, grab lunch and begin our drive to the Hoover Dam. **drive time - 3.5hours. Hoover Dam visit then head to Vegas to visit family and sight see for a few days.
Day 4 - Vegas
Day 5 - Vegas

Day 6 - Leave early and drive to Death Valley **drive time - 2 hours. Spend the entire day at Death Valley then drive to Sequioa NF **drive time - 5.5hours OR Skip Death Valley and save those 2 hours of driving and go straight from Vegas to Sequioa **6hours**
Stay 2 nights at Sequioa.
Day 7 - Sequioa
Day 8 - Leave Sequioa and head to Joshua Tree National Park - **5 hours (maybe leave in the middle of the night so kids can sleep?)
OR skip Joshua Tree and Palm Springs and head straight to San Diego
Day 8/9 - Joshua Tree to Palm Springs for the night
Day 10 - Leave palm springs and either do the detour (1.5 hrs) to see Mt. Jacinto) or drive straight to San Diego . **2hrs**
Day 11 - San Diego
Day 12 - San Diego
Day 13 - departure from San Diego back to Florida

Questions
- I am not so particular about visiting certain places as I am about the topography/landscape for the children to experience. I would prefer to cut back on the driving if any of these parks (between Arizona, Nevada, and California) overlap a lot in features. I am pretty set on seeing Sequioa since there's nothing else like it, but flexible with other landscape (dessert, canyons, boulders, etc). So what do you think I can cut out to help cut down on the driving time, if anything? I am a little afraid of this being an exhausting trip and the kids getting desperate with so much driving.
-Would you skip death valley and go straight to Sequioa from Vegas.
-Would you stay 1 or 2 nights at the Sequioa forest?
-Would you stay 1 or 2 nights at The Grand Canyon?

HELP. Any guidance would be greatly appreciated!