Hi everyone, thanks for the advice. I completed the Camelback hike, starting at around 07:10. I ascended using the Echo Canyon route, and descended using the more gradual Cholla Trail. It was fun - and quite a bit steeper than I thought. For a brief moment, I almost lost my footing on the way up.
I brought five 500 mL (approx. 17 oz) bottles of water - I drank one on the way up, and one immediately after I finished the descent. I then walked about 13 kilometers (8 miles) to Old Scottsdale, and then the ASU Tempe campus (I drank all the water I had on me, and bought several more bottles). I was prepared to take the bus or call an Uber if I felt weak.
Overall, this was a pretty tough half-day of walking for a Canadian who isn't used to this type of heat. I wish I could have tried the Flatiron hike, but maybe another time.