Hi scullaf,
I have been advised that the morning of your final day is at leisure so there should be time to do a flight over the Hoover Dam and Grand Canyon - the only thing the team are concerned about is, what time it is due to finish with the lunch on the canyon floor. We would recommend that you check what time you would be back at the hotel before booking just to make sure of the logistics. You would need to be at the airport 3 hours before departure to check in.
Kindest regards,
Julia