You have to live your life. Sure, the warning is something that most people will think about getting on a plane or going to a place that is an American icon like WDW or NYC, but you can't let fear rule your life. Back in 1999, on a spur of the moment decision we booked a WDW day after Christmas through New Years trip 3 weeks ahead of time because we wanted to have something to remember when the calendar rolled from 1999 to 2000. There was 1 room left on property due to a cancellation- which I would bet was someone that was scared off by all the Y2K hype and warnings of terrorist attacks planned at multiple high profile public places for that New Year. I had friends that were shocked that we were getting on a plane and going out of town for Y2K, and my mother was not exactly pleased. WDW even put flashlights in everyone's room on New Year's Eve in case the entire power grid went down and all electricity was gone as some predictors said could happen at Y2K. Well, absolutely nothing happened and we had an absolutely fantastic trip, including a fabulous New Years Eve at WDW's then Pleasure Island extra ticket party. It was a terrific way to end the 1900s!
20 years ago when I saw all the news reports of that kind of thing, I thought that nothing like that could ever happen in my little low profile area of the country and that we were totally safe from anything like that at home. Well, I lived in the OKC area and was about 4 blocks away from the 1995 explosion when it happened. I didn't see the building, or the area, or some of the injured people for the first time on the news, I saw them with my own eyes. I learned then that bad people can do bad things anywhere, so there is no point in letting fear of that kind of thing stop you from living your life. Actually, that is probably one of the reasons why we didn't hesitate about booking the WDW trip on Y2K.
Sure, you would think that WDW would be a target, but if you look at the Paris attacks- they were not the big target places that you would think about. Instead, they went for places that would not be considered big targets and which would have much less security. It certainly makes sense to think about it and have some concern, but I wouldn't let it spoil my fun!
Have a wonderful trip!