Thanks to everyone who contributed with advice before!
The motto of the trip was: why choose one or the other, when you can do both if you just get up early enough?
For now, just the facts: 1000 miles driven
Day 1. Grand Canyon
Down to the canyon, across 2 suspension bridges and back up (down South Kaibab and up Bright Angel Trail)
5am wake up time, 16.3 miles, 4420 foot elevation gain, 7:45 hiking time (excluding lunch), 54F temperature at the top, 85F temperature at the bottom
Finished up with a shuttle ride on Hermit Road and a short hike there
Day 2. Zion
Trip to Heaven (Angel's Landing, a top of the world suspended in the middle of the canyon, the one trail I chickened out on 4 years ago), Emerald Pools, Riverside Trail
5am wake up time, 10 miles, 1750 feet, 5:30 hiking time
Day 3. Bryce and Kolob Canyon (Northwestern Zion)
Queen's Garden, Peekaboo, Two bridges, Timber creek overlook
4am wake up time, 9 miles, 5:00 hiking time