Of course your father should be allowed to do what he wants. He is a grown-up, mature man. Not letting him out sounds like abuse of power.
The simplest solution might be if your father, the staff, and you and your siblings meet and try to find a solution which everyone can accept, and in particular one in which your father is happy. It might be a wise idea to consult a lawyer before this meeting, to discuss the legal rules regarding these kinds of issues in your country.
Good luck in your efforts to give your father the life he wants.