Predestination can exist even if there are infinite choices. Look at it this way... You are only what you are made of. There is no external or "other-worldly" part of you. You are solely what your DNA makes you regardless of what religion tells you, without evidence I might add. Far be it from me to stick clear from speculation and stick to evidence-based scientific fact. Therefore, even if we have an infinite number of choices, we will always choose the one that we choose.
Like I said, we are what we're made of. Therefore, there is no exterior force deciding what we do. Our actions are our own and they are internal. This is free will.
However, you cannot break your own free will. That is the restriction on it. You are free to do exactly what you think is the best (consciously or subconsciously) and nothing more. Free will is your internal decision-making process and no external forces can impact that decision-making process in the grand scheme. Therefore, the decision made will be singular in intent, that of free will, and nothing more.
You are restricted in this way. You cannot interfere with free will. Therefore, your free will is predestined by the content of your internal decision-making process. This is predestination. Predestination and free will are the same thing. You are predestined to chose a course of action but it is of your own free will that it occurs. Free will and predestionation can co-exist and do because they are the same thing.