There's a theory that there are an infinite number of parallel universes out there. Basically every time we come to a decision point and turn right instead of left, the universe splits and and there's a version where you turned left. So if in infinite realities we've done it all, then we have the free will to make our own choices.... And every destiny will come to pass somewhere.
I've also heard a similar theory about God and creation. At the moment of creation he saw every possible path. So we have free will, but no matter what we choose, God knows where it leads. Free will and predestination wrapped up in God's mind.