I dont think they will, ground targets are not as easily affected. The bombs that were thought of for the uk - us flights were very small yet would be enough to bring down a plane because they are so delicate. In an open space it would hurt the people directly beside it, as in one or two feet away.
Hopefully they aren't so paranoid as to escalate security to such a degree. Cars are a lot more dangerous than the type of binary bombs that water bottles and such can be used as. Even talk of this saddens me greatly. Terrorists are awful and vile, but please try and remember that this is the reason they engage in their activities and it is so much more likely to be killed in a car accident then to fall victim to one of these disgusting attacks. Of course some precautions must be taken, but there are limits. The surest way to stop it is catch the would be terrorists, not protect ourselves with a million inhibiting securities that can only stop a particular method.
In response to the original question, I'm sure if Disney makes such a move they will widely advertise it as will cause great distress and expense to many that visit their parks.