Tucson to Sedona will end up being closer to 4 hours due to having to drive around Phoenix.Thanks for the input.
My daughter is 11 and a pretty active hiker. Definitely trying to do all the research I can, though, to make sure we're prepared for every hike we attempt.
All of my in-laws live in Tucson and I am down there a few times a year. I have always enjoyed the Sonora Desert Museum and you'll see plenty of saguaro driving through the pass from Tucson. They even have a cacti garden at the museum with lots of different varieties. On your way back, grab a beer at Pueblo Vida and take your kid to the outdoor mercado (San Agustin) to eat on the patio at Seis (get the fried avocado tacos and chicken taquitos). More hiking would be Sabino Canyon and Seven Falls, Douglas Spring and Tanque Verde Ridge.
Outside of Sedona, hike up West Fork trail. It isn't difficult but you get to see the red rock canyons and get to cross the creek a bunch of times. Our cabin is just up river from the entrance and I've been up there tonnes of times. Your kid will enjoy it. Closer to Sedona townsite, look up Soldiers Pass. I usually hike it as a loop to see the seven sacred pools, the Mitten, Brin's Ridge, Hole in the Sky, etc.
If you make it up to Flagstaff, hit up Dark Sky brewing and take your kid to Lava River Cave. Not hard but neat to walk a mile in a lava tube, bring a flashlight!