I'm sorry but you don't have a claim.
Defamation of Character requires that a person transmit false information about the plaintiff which hurts their reputation and causes them to suffer losses. For example, a person telling people that you are a thief, a liar, or a racist would be defamatory.
You don't have a claim for emotional distress either. Intentional Infliction of Emotional Distress requires something that shocks the conscience and causes a person to suffer extreme and severe distress, often requiring counseling. An example is usually when a practical joke goes all wrong and the plaintiff is emotionally damaged. There's also Negligent Infliction of Emotional Distress but that requires some kind of touching.
Under Florida law, grandparents have virtually no rights when it comes to their grandchildren. It is within your son's lawful rights to prevent you from having any contact with his children.
This is not to be considered legal advice nor does an attorney-client relationship exist.
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