After a couple of overtemperature events on my iPad while flying, I decided it could use a little cooling off. I chose these objectives for the design:
The hot locations on an iPad Air2 are at the bottom connector, when charging, and on the right side, where the cpu is doing its work. I usually run my iPad in landscape orientation so I chose to add a small fan along the edge near the CPU location. Even a low air flow can improve convective cooling. Any airflow is better than none. I chose a 40x40x10mm fan that operates at 5VDC so that it could be powered off the iPad charging cable. The fan current was measured at only 60mA, so this is not a significant draw on the USB power source. A simple mount was created in SketchUp that slips over the locking tab on the side of my iPad case. The fan mount was printed with ABS since PLA would easily deform if exposed to too much heat or sunlight. I later added small standoffs to raise the iPad viewing angle and give better inlet flow. I've used this for a couple years and have not seen an overtemperature warning. Of course, it pays to keep direct sunglight away from the iPad as much as possible, as well.
This should give you a place to start with your design since you can pick up my SketchUp file and work from there to fit your installation.