Well Ricky I do see one big upside to your plan. When word gets out about the "disobey", be over 60, not be useful = get shot you probably won't have many refugees knocking on your door.
By the time people figure it out the initial rush of refugees will be over anyway. Plus having a smaller amount of people is beneficial. There is only so many people that a military base could handle before it becomes chaos. Also the whole thing of people in crowds becoming stupid and acting irrationally.
Logically having a plan like this makes the most sense but I hope I wouldnt ever have to go through with something like this. It would ensure survival but at what cost? I would become a tyrant.
Hopefully there is some sort of higher military command instructing everyone what to do before communications fall out.