The steps I am not sure about, probably more bag checking.
If someone wants to blow up or posion-gas disney world then they will.... There are enough entrances and exits into the park that they will get in, the security checks are a placebo, IMHO, and would only catch unprepared nut-jobs trying to perp a crime. The real terrorists would be able to get in no problem.
What might be a better question is whether or not you consider Disney World to be a viable target: It does amass large numbers of people together, it is inextricably linked with the nations economy and communications industry (lest we forget who owns ABC and ESPN) and it is a national icon....
BUT- Disney World is not an economic institution with just employees and management of a large corporation, it is a park filled with almost exclusively families. The terror war is also a battle for world sympathy, the two towers/pentagon/white house(unaffected target) were celebrated through a lot more of the world than you would be comfortable with, as they were symbols of American paramountcy, power and corruption. Disney world would not illicit the same effect. It is instead a symbol of american family values and recreation. If I were a terrorist and wanted to attack an american institution which would help rally people to my cause, I wouldn't choose Disney world, I'd take another stab at the White House, John Hancock building, Sears Tower, UN headquarters, or an american airbase or missle silo. Attacking disney would provide world coverage that would do more damage than good for them.
Sorry if this reply seems callous, but as a non-american (Canadian) I can be objective about this situation.