Set RTH to hover.
Your best situation is one where VPS can function so you have positioning and hover stability. This will keep you out of ATTI mode where the drone will behave like an airhockey puck rather than a shoe sole on pavement. If you have no experience flying ATTI, don't... you WILL crash. Oh, and look like a total fool for your demonstration
Make sure the area you're flying in has clear, non-uniform surface below that the VPS cameras on the bottom can see moving. If your flying over a uniform concrete floor, use some masking tape to lay down some contrast stripes. 6ft apart, test it, add more in between as necessary. Depends on how high you'll be flying.
If your flying all around the hangar space, other objects (racks, boxes, shelves, fork lifts, chairs, airplanes, etc. etc.) will do the job – as long as there's sufficient lighting. There usually is in such a setting.
If not, well, learn to fly ATTI