Add the hike to Delicate Arch in Arches to your list.

Overall it is a good plan. There are so many wonderful things to see, you will find yourself enjoying it all.

There are a few tweaks I would do.
Day 2, I might just head to Kolob Fingers Canyon first rather than go back out to I-15 later. You could do this if you have the hotel already. There are many in Springdale which are good and that is a nice place to stay when visiting the park. You might still have time to take a shuttle ride into the main canyon that afternoon/ evening which I would recommend just to get an overview of what it there.

Day 3, The Narrows is a difficult hike due to the nature of the river bottom which is covered in large ballsize rocks. But it is a fabulous hike and I would highly recommend it. Go to Zion Adventure Center to pick up some boots and hiking poles which will help. Then just go as far as you feel comfortable with. Orderville Canyon is 2 miles up and can take 2-3 hrs to get to. You don't have to get far to enjoy that unique area.

Other hikes to enjoy would be Emerald Pools, Hidden Canyon, or Pa'rus. I would leave the Canyon Overlook and other side of the park for the next day so you aren't backtracking.

Day 4, Do the Canyon Overlook trail in the morning. It is better in the morning light. Enjoy the drive out of Zions. Take the time to stop at Red Canyon on the way into Bryce. Even doing those two things first you will still have time for the scenic drive and Navajo/Queen's garden loop trail at Bryce.

Day 5. In the afternoon you could check out the Fairyland Loop. You don't have to do the whole hike. Or go to Mossy Cave. OR you could drive up to Torrey along scenic 12 and spend the night there.

Day 6 I hope you plan to go via hwy 12 through Capitol Reef???? Get lunch in Green River so you can stop and see Canyonlands Island in the sky and Dead Horse Points first before getting all the way to Moab. You can see these fairly quickly, an hour for DHP, and a couple for Island in the Sky- Mesa Arch trail is the only one there that I feel is essential. (Skip the drive and hike to Upheaval Dome but be sure to stop at the Green River Overlook).

Day 7 Doing the other parks on day 7 will allow you the whole day at Arches and you will use it. Park Avenue, everything in the Windows Section, Landscape Arch and Delicate Arch are all great hikes to do. (bring a picnic cooler basket to eat lunch in the park- no concessions here)

Day 8, Assuming you will be going I-70 to I-15. On the section west of Green River be sure to be on the lookout for pull offs (not even rest areas or anything, but you'll know when you want to pull over) for the fantastic views of the San Rafael Swell.

On Day 7, I meant doing the other parks on Day "6" will allow you all day for Arches.

I didn't think that "The Narrows" difficult at all. The rocks are slippery and that is something that a person isn't used to. You certainly could slip and fall(we didn't). I would rent the shoes and/or pants for the hike. Check with Park Rangers before hiking. You don't want to be in this if there is rain anywhere in the area.

If you can do Navajo Loop/Queens Garden you can do the hike to Delicate Arch. Having been to almost all of the major areas in Utah twice, Delicate Arch leaves the biggest impression on my mind.

Stop at The Gifford House in Capitol Reef for pies

Stop at Goblin Valley on your way to Moab.

Thank you so much for all the information. This is great!
Will add Delicate Arch and go for The Narrows if the conditions are good.
I have to get a road map and plan all the drives. I do want to take Hwy 12 (everybody says it is such a scenic drive). I don't know if we'll have time to stop at Coral Reef NP; but I think InSandy's suggestion to do Canyonlands on day 6 sounds great. And we will stop for pies at Gifford House!!!
I am still trying to decide on spending the 2nd night near Bryce, or move on to Torrey. On one hand I feel we would be more relaxed if we stay 2 nights at each hotel, but on the other hand, it would save an hour drive on the long ride the next day and I've also heard that Torrey is quiet nice.

I would consider flying into and out of Salt Lake City. It's a much shorter drive back from Moab.

Also, if you did that you'd have an extra day since you wouldn't spend a day in Las Vegas.

I would do canyon Overlook on the way out of Zion going to Bryce.

Plan on getting up very ealry and going to Bryce Point for a spectacular sunrise.

Yes, add Delicate Arch hike to be there an hour before sunset. Amazing as it turns orange in the setting sun.

Rather than Torrey you could consider staying in Escalente. There are a few nice, reasonable motels there.

There is something nice about spending two nights at the same place. However, shortening that ride is a good idea if you can.

I always try to plan at least two nights at each place. However, last year I went to Utah with my daughter for 3 days and we stayed at 4 different places in four nights. For a short trip it wasn't bad. We just didn't unpack at all.

My brain was turned off. I read Torrey but thought Tropic.

Torrey is a good idea but quite far from Bryce.

It is about 2.5 hrs from Bryce to Torrey. So you could save more than an hour the next day on the drive to Moab. With you having seen Bryce the day before and the horseride in the morning I'm not sure what else you would need to see at Bryce, so it makes sense to me to get on the road and give yourself more time in the Moab area the next day.

The pies are directly in Capitol Reef, which is pretty much right on HWY 12. I wouldn't suggest any hikes there, but do stop for pies. They have them in the mornings, but are usually out of them by the afternoon. Eat them at what I think is one of the very best picnic areas in a National Park. The picnic area is right next to the Gifford House.

I would suggest staying at Austin's Chuckwagon in Torrey.