UPDATE: I checked the coolant there's a leak in or around the radiator. I added about a gallon (it was 50% low!). I then took the Honda Pilot for a 25 minute test drive with the A/C on full cold. The AC works great, and continued to remain cool when stopped and on the highway. It appears that with the vehicle temp rising (when the coolant was low), the A/C shut off.
There's definitely a leak in the radiator, as I can see the Honda blue fluid on both sides of the radiator, and splashing around the lower hoses.
Now I just need to decide if I should let the dealer handle this, or if I should replace the radiator myself.