All the places you mentioned are amazing but there is a lot empty land between them. The desert is beautiful but it does get a little old after staring at for a couple of days.

Most of the more interesting places to see will be in California and most of that near the coast. I highly recommend Monterey Bay, rent a kayak and paddle around the bay, sometimes otters or seals will come play with you or go out on a whale watching boat though I am not sure what the season for that is. DO visit the aquarium. Just driving up highway 1 is a pretty drive with lots to see. I am not the big fan of San Francisco but most people like it. I would prefer to keep driving north across the Golden Gate Bridge and up 101 through the Russian River valley then cut over to the Armstrong State Redwood Reserve. If you have never seen a giant redwood you need to, they are impressive. Plan on hitting some of the wineries while you are there and come back along the coast on highway 1 just make sure you have a full tank of gas. Researching restaurants in area is also a good idea because there some very nice ones. I really like the Tide Warf restaurant in Bodega Bay.

The Grand Canon and Vegas are pretty cool and Vegas runs 24 hours a day but the best shows are at night. If you make it far enough east try hitting Mesa Verde but plan on it taking most of a day. Also don't rule out heading south to San Diego and if you do hit the zoo. If you have never been to Mexico you can dip down to TJ but I wouldn't bother. You can see all the Mexicans you want right there in San Diego.

Driving in the American West is a bit of a marathon event and 10+ hours is not unheard of. If you are game the best way is to drive at night and sleep in shifts. It is tiring though. I drove from the coast of North Carolina to Dallas Texas straight through, about 22 hours, but I don't recommend it.