What you could do is make sure you are awake at the time and make sure they have your phone number so that they could call you can you could arrive at a moment's notice to thier location. The odds of them all being questioned about your id at the same time are quite unlikely. If the worst happens, the odds are that you will have to go from place to place as you are needed, one after another. But if the worst should happen you need to be prepared to arrive there at a moment's notice. I would call all 3 of my buddies to determine who is the closest person to the register. Then prepare myself to be at that location first, then the next closest second, etc.
Hope this helps!! And most definitely I hope that you do not have to do all this!!! However if you do I hope it helps!