The US Federal Emergency Management Agency (FEMA) is responsible for the coordination of the response to a disaster that has occurred in the United States that overwhelms the resources of local and state authorities. You need look no further than New Orleans after Hurricane Katrina to see that they don't always do a great job in their core area of focus. One of FEMA's other roles is education, and that's rather interesting as well.
On the FEMA Kids pages, FEMA offers "A Scary Thing Happened" a "children's coloring book to help cope with disasters." The lead image at the beginning of the book, and also featured on Page 12 is New York on 9/11. The first page already comes helpfully colored in so you get the general idea of what to do. Page 12 however is left for kiddes to color in at will (see above.)
Apparently though coloring in 9/11 is all ok because it's all about kids understanding they weren't to blame that airplanes crashed into the World Trade Center and The Pentagon. Oh, if they're involved in a disaster, they book advises they should wait two months before seeking professional psychological help (seriously.)
You can download it from FEMA kids here.