I've done similar there-and-back type trips myself. LA-Phoenix and SF Bay area-LA in my case. If you make sure your trip fits within your routine waking and active hours as much as possible it's much better. Working around hellacious traffic might require stretching it some, though. Fuel and food stops should be fast, 10-15 minutes, especially if you want to take time to see something. I rest for half an hour or so after arriving just to shake off the road before heading back.
Figure 12 hours minimum, with good traffic and no sight-seeing.
Mostly, you'll be seeing whatever's visible through the windows of your vehicle.
One quick stop would be at the concrete dinosaurs in Cabazon. A fun stop, with a chance to get some fuel and snacks or have an iced tea at the Wheel Inn restaurant.
If you want to see the windmill farms close up, get off at Whitewater just beyond Cabazon. Take the road paralleling the freeway, (which is old Hwy. 99) past Whitewater Rock & Supply, (maybe a mile) to where it ends in a dirt road going uphill. That takes you right up in among the windmills. The roads are public and well maintained, and go right next to the huge machines. A great view of the mountains too, especially San Jacinto. It's a short diversion, and you can go back the way you came, or go through the farms down to Hwy. 62, then back a mile or so to the 10.
When you come up out of the Coachella Valley there's the Patton Museum at Chiriaco summit. That's where Patton's tanks trained for desert warfare in WWII.
Just before Chiriaco is Cottonwood Springs Rd., which is the south entrance to Joshua Tree NP. Maps and info are at the Visitor Center. Don't worry, you won't get lost if you stay on the paved road. At first it's not as scenic, being still low desert, but two hours gives you time to get to the higher part where the Joshua trees are, drive around, get some pictures and get back down to I-10.
Worth it if you've never been there.
Lots of desert between there and Phoenix. At Blythe, you could stick your toes in the Colorado River.
I used to live in Phoenix. Can't remember much worth seeing, though.
Tell me what time you're coming through Redlands and I'll wave in the direction of the freeway. Unless you're on the 60-then I'll wave the other direction.
