A very interesting question. You don't say which country the set is in or whether it is a closed or outside set. You also don't mention the type of RPA you plan to use. However, I will give you my two pennyworth.
Before you can educate the crew to the dangers you must know yourself what could go wrong and what the consequences would be. You need to carry out a full risk assessment and, where the risks are high/unacceptable, what you can do to mitigate them. The hazards of using an Inspire close to people are great - the blades alone can cause severe lacerations and serious injury or death. Do you need prop guards? Do you need to tether the RPA so that it can not come into contact with the crew/cast? How stable is the RPA indoors or in windy conditions? How accurately can it be flown? Has the Pilot got the skills to do the task and to act correctly if something goes wrong? Do you have an observer and that essential extra pair of eyes?
In briefing the crew/cast you may wish to consider some of the following:
- Don't distract the Remote Pilot.
- Don't move outside rehearsed positions.
- Don't try to reach out to or touch the RPA.
- Stay clear of the main and standby takeoff/landing sites (min 30m in UK).
You could go on. You must above all ask whether what the director want to achieve can be completed safely.