Have a couple of recommendations regarding photo stops:

1. Antelope Canyon Best times for guided tours are between 10AM-12noon. Try and reserve a photo-tour which is longer and totally worth it.

2. Horse shoe Bend, near Page, Arizona. Short hike to get to the overlook, amazing view.

As you may already know, that time of the year is usually very hot in the GC area, we did somewhat of a similar trip last year. Drink lots of water.

Thanks, but we will only be in Bryce, Zion, and NR GC

It's really photo-ops country. We just did it (see trip report under Utah) - with the exception of getting to the North Rim which want to do next time.

Was just checking the milege to the North Rim - and it's a doable one day round trip from Zion, but will involve some driving.

For Bryce - check out the first 4 stops in the Canyon (Sunset, Sunrise, Bryce, etc) for great shots.

For Zion, my favourite photos came from Rte 89 around the tunnel, and the Canyon Overlook Trail just beyong it (which is a moderate hike, steep but short). The Checkerboard Mesa is also amazing, if you are taking that route east. The stops on the shuttle bus, such as Court of the Patriarchs, gave nice light about an hour after sunrise. I didn't get all the way up Angel's Landing, but there were lovely views of the valley from the top of the first switchbacks.
Some of my pictures are at the link on my trip report (click my screen name).
I didn't go to Bryce, so can't help there, but the GC & Zion are wonderful.

I find the best place to get ideas for photos is by searching on http://flickr.com. I spent hours one night looking through a Grand Teton group and getting ideas.

I highly recommend picking up a copy of Photographing the Southwest, by Laurent Martres. There's one volume for Southern Utah, and one for Arizona.

I think you have budgeted too much time for Bryce. It's an impressive place, but I think you can easily finish seeing it in one day, or even half a day. The best light is around sunrise. You'll want to check out the views from up on the canyon rim, and also hike into the canyon. For the rim views, I think you don't need to do more than walking the paved, flat part of the rim trail between Sunrise and Sunset Points. You might also consider a quick stop at the Natural Bridge Lookout, but one can use up a lot of time driving out to the more distant lookouts, and I don't think there's much more to be seen there.

For the hike into the canyon, I'd suggest the Navajo/Peekaboo combo, if you have that much time and energy. If not, then the Navajo/Queens Garden loop, which is somewhat shorter. Or just the Navajo Loop, which would be the shortest of all. I find the Queens Garden loop to be rather dull, but it is the least steep way to get into and out of the canyon. The most impressive thing to hike through is "Wall Street," which is at the start of the Navajo Loop, but note that it's a long, steep ascent on switchbacks. You might want to consider hiking down it instead of up it, even though the "recommended" direction for the Queens/Navajo loop goes the other way.

At NRGC, the views from the lodge are quite good, and there are little lookouts that you can walk to nearby that are pretty impressive. I tried walking a little farther along the rim trail from there, and the trail quickly moved back away from the rim and behind some trees, so that I could no longer see anything. I haven't actually hiked into the canyon from the North Rim. Be sure you make it out to Point Imperial. There's also the Ken Patrick Trail that connects Point Imperial back to the Lodge. It's long, and you probably wouldn't want to hike the whole thing. But the part near Point Imperial should provide some nice peace and quiet and great canyon views. I haven't done it myself, but it has been recommended to me.

Another thing to consider: I find that I'm quite affected by the elevation at Bryce and NRGC, for the first 4-6 hours or so after I arrive. It's not scary or anything, but I tend to feel kind of sleepy and not interested in hiking until my body has adjusted.

On our first trip to Bryce one hike we enjoyed was one I'd read about in a hiking guide. We were staying in a cabin in the Park, and caught the free shuttle from there to Bryce Point. From BP we hiked back to our cabin along the Rim Trail (not to be confused with the Under Rim Trail). The Rim Trail continues farther north, ending at the overlook at Fairyland Point. We didn't have time to do the whole trail.

The part we hiked took us past 3 of the main overlooks - Bryce, Inspiration, and Sunset Points and it's easy to continue to Sunrise Point, which we did. Hiking along the trail we saw things we would have missed if we'd just gone to the various view points/overlooks. Managed to get some interesting photos along that hike. There's not a great deal of elevation change so it's a fairly easy 3 mile hike. From where we ended, it's another 2.5 miles to Fairyland Point. Next time we go to Bryce we'll figure out a way to do the whole trail.

Enjoy your trip and safe travels.