How to release paper airplanes at 100 meters?

We want to organize a competition for 12 year old kids to build paper airplanes. We would then lift them to 100 meters with an IRIS plus and release the airplanes to see which ones fly the furthest.

Does anyone know how this can be configured with the Pixhawk and the IRIS+ transmitter/controller?

I think connecting a servo as described on this wiki page should work.
copter.ardupilot.com/wiki/common-servo/

I’ve used this method for a ball dropper for AVC a couple of years ago and it worked fine (my copter is shown in a video on that page).