"A terror attack may be imminent" - what do we say to DGC?

Having seen that the terror threat level has now been raised to the highest level and they're talking about the military being on the streets and at big events, how are we supposed to feel about it? TM said not to be scared, that the move was a proportionate and sensible response and I'm sure she is right, but what do I say to my DGC? How can we help our young ones through this and prevent them from growing up terrified of the world they live in? I don't want to pass on my feelings of helplessness.