A suggestion regarding Bryce Canyon
Hello:
I agree with everyone, regarding the route you seem to be leaning towards. The drive between Capitol Reef and Bryce is epic, one of my personal favorites, with sweeping views, gorgeous curves, and not all that much traffic. If you're going to stay the night in Tropic, you should make a point of getting up super early--before sunrise, if you possibly can, and drive straight to Bryce Canyon. Depending on where you stay in Tropic, it's only 20 minutes away (or less--there are several motels right at the park entrance). The gate doesn't open until 8 AM, but all that means is that nobody will be manning the entry station. Unless things have changed since I was there two years ago, you can drive straight into the park; there are (or were) no closed gates across the roadway. Once inside the park, there's a drive that leads past a series of overlooks, each with a parking area. Start at Inspiration Point, which faces due east: Bryce Canyon has an eastern exposure, and when the sun pokes up above the horizon, it sets that entire landscape on fire, spires and hoodoos gleaming in golden light! As a photographer, you'll truly appreciate the very special opportunity. The best part about the early start: you'll have the whole place (almost) to yourself. Once the gates open and the tour buses start rolling in, it's a completely different experience. Assuming you have an annual parks pass, it's perfectly acceptable for you to drive in without paying. If you don't have a pass? You can pay on your way out.
I have a slideshow on my personal website with photos of what I've just described. Check it out, if you're interested (give the first page a minute to load, then the slides will advance automatically):
Bryce Canyon Sunrise
Enjoy! Sounds like you're going to have an awesome trip!
Rick
A few ideas for quick stops.
I would slightly disagree with glc about heading to Cedar City after Bryce, although it's personal choice. Now if you are camping lodging costs wouldn't be much of an issue and I would get on to booking the Watchman campground in Zion NP. I would actually head south on US89 after UT12 to Mt Carmel Junction and take UT 9 through the Mt Carmel tunnel. It's a fantastic drive into the park and the chance to stop to take in some rock formations at Checkerboard Mesa.
Here is a list of stops west of Denver that spring to mind and don't take long to enjoy.
I-70. Take US6 detour to Loveland Pass. Great views as you cross the Continental divide at around 12000ft.
Colorado National Monument Rim drive between Grand Junction and Fruita CO. (Not so quick and likely to add 2 hours with stops but a great detour)
Goblin Valley SP between I70 and Hanksville UT24. Great rock formations but again would add a couple of hours. (Cool Gas station in Hanksville called Hollow mountain. Store has been created by blasting a hole in the rock and it may be a good place to fill up)
Capital Reef NP. The scenic road is great if you have time. If not, Gifford Homestead is a neat stop and you could stop at Panorama Point and Goosenecks overlook just to the west of Fruita UT.
When you join UT12 about 20 mins south there is Larb Hollow overlook. Lovely views for a 5 min stop.
Just beyond Tropic UT you will see parking for Mossy cave trail. The cave isn't much tbh but it offers a nice 15 min stroll in a quieter part of Bryce. When you leave Bryce you will eventually go under Red canyon Arch that spans the road, just after there is parking and you can cross the road and walk among the red rocks.
As mentioned, Checkerboard Mesa if you take the Mt Carmel route to Zion.
Death valley quick stops. Zabriske Point, Furnace Creek and the Sand Dunes.
Tioga Pass (CA120) As you enter the road from 395 you will see Tioga gas Mart. If you take the turn and continue up the hill past the station you will come to a parking lot with expansive views of Mono Lake. You could stop and stroll at Tuolumne Meadows and also pull up by Tenaya Lake.
These are just a small sample of options and you won't get time for all. You need to get a few more days !! lol