What errors did the family make?
Having played with my children on that exact beach, I made a couple of significantly different choices from the ones made by there parents. I don't entirely blame them for not knowing how to stay safe in an unfamiliar state, but I don't think it's appropriate for parents to blame Disney after a wild animal attack.
My kids were not allowed in any Florida water that was not clear, until they were adult-size, and that includes the water that was "a foot deep" (probably five or more feet from dry land) where their son was playing. Also, for watching fireworks or outdoor movies, I always make sure there is a significant amount of clear, gator-free space on all sides, preferably a significant step up between my kids and the water. I've been stalked by gators in several spots where morons have fed them, and I am always cautious about that risk when in gator territory.