thanks for you questions.
There is no automatic way by now to play videos, when a group reaches a GPS location.
What you can do is to add an information screen after reaching the GPS location (which is mandatory), and implement the video there.
You make the Bound as private Bound which is only accessible with a password or a QR-code. This is at a cost of 7€. You can find this feature as the secret Bound feature on your Boundpage.