Hi. Reading the description, i guess the the idea is to enable or not the tracking code depending on the cookie choice, it should be easy to add ( its some javascript for google analytics, facebook or similar i guess ).
Not much sure what you mean about the third button, if its like - the initial buttons show on separate page that shows up when there is no choice made and not cookie set, so this kind of says - i will decide later - and allows temporary access to the website (with tracking disabled, and in some sense same thing as if user selected - Disable tracking , just probably this will expire with the session and user be asked again next time)...