FThe manager has a huge say. He's the one who runs things day to day. If the manager still wants him, Kaka can stay knowing he'd still play for Milan
Not at Milan. Ancelotti has very little to say and he does not make any key decisions.
Milan can accept the bid and they probably should given the large amount. But after that Kaka can easily say I don't want to leave. If he does move, it will be completely his decision. He's not being forced to do anything, let's not delude ourselves.
You're the deluded one if you think that if Kaka moves it will be entirely because he wants the money and wants to move. If Milan decide to sell him, they will ask him to leave and he will have to obey.