I can see plus and minuses on both sides of the questions. But when stacked up, I personally don't think it will be a morale booster for the people who need it the most. There is no gasoline, there is little food but no way to get through to the grocerywhen there is. People, thousands of people are living in emergency shelters and are worried sick (as we all would be). The police even did a welfare check on Adelaide because a close friend couldn't contact her and knew she lived close to some of the worst examples of the disaster.
Money is starting to flow in and that is the most important morale booster at this stage and because of the damage, building and other related trades as well as additional supply help will soon begin to expand, unemployment may well for awhile at least, drop like a stone and to those needing employment, that will be a God send, not to mention they'll have income to clean up and rebuild!
Therefore I have to agree with Trip that while New Yorkers are a hardy bunch, I can't see how the Marathon could raise morale as that will be the last thing people in tragic circumstances will think about, especially since most won't only be unable to watch it even on TV, but have far more important things on their minds. As Trip also pointed out, the security and housing will have to even a small degree, an effect two of the things the people who live in New York need the most; food and housing.