One thing I read once and applied to my last dog and my friend has done with his: use as the hand gesture for sit bringing both your hands up to your chest, like kids do when afraid. Dogs tend to respond to visual commands as much as or more than vocal. This way if someone is scared of the dog and makes that scared gesture, the dog will (in my experience in most cases) sit.

And in general, consistency is the most important thing. In the end, teach your dog whatever commands you want with whatever cues you want, but consistency is the key across the board. This includes initially how anyone interacts with your dog during the initial training phases, if possible. This helps reinforce the specific training you're doing and that not just you should be able issue commands