Using the reasonable man concept, it think Disney made reasonable efforts to protect the guests. There are signs that say no swimming. Putting up signs about gators would cause fear amongst every small child that visits.
It is also reasonable to say that alligators are native to the area, and they pose a danger in anybody of water.
That said, it is a horrible accident.
1. All of the bodies of water around that resort hotel are man-made and are part of the resort, which means they are held to a higher legal standard than if the hotel was on a beach along the Atlantic Ocean or a natural lake.
2. Legally, a resort property must provide protection and warnings to their guests commensurate with the local knowledge that their guests could reasonably be expected to have. This means that a resort catering to local visitors can reasonably expect its visitors to know about local weather and wildlife. A Disney resort, on the other hand, is marketed across the entire globe to potential visitors who don't have a clue about the local dangers in that area.
Interestingly enough, the lawyer also said that Disney's own insurance carrier (or their internal risk management team, if they are self-insured) is probably down there right now going through the entire resort to identify hazards, and coming up with a plan to get rid of the alligators or drain the lake and canals.
I don’t think that putting up signs warning of alligators would cause most young children to worry or be afraid.
Kids the age of this one can’t read anyway, so there’d be no issues.
And the ones who can need to learn appropriate caution.
The world cannot be made a perfectly safe place and you can teach children reasonable caution without instilling fear in them.