These are still highly populated areas, given the scope of weaponry they are threatening to use. They could do it on a Sunday night at 2 a.m. - the economic devastation would still be enormous and change our way of life, maybe forever.
That said, I've come to the realization that I just have to trust in God...
Definitely. Times Square, the theater district and most of midtown is packed even on the weekends. Also, given that it's a holiday weekend, people do take off and head for places like casinos. There are as many people concentrated in those large hotels/casinos as there are in an office building on a work day.