God knowing what will happen - by virtue of being present to observe it happening - doesn't prevent a free choice being that which determines what happens. If free choice chooses something else then that is what God would observe happening and by virtue of that, will know it "beforehand". God simply observing doesn't affect a free willed being ability to choose.
This is a major point of argument in Philosophical circles. I would disagree with you.
Let's say you're born and God knows that when you turn 20, you'll turn left at a particular intersection. You go through your life and then, when you're 20, you come to the fateful intersection. You are presented with an apparant choice: turn left, turn right, or got forward. Now, knowing that God
knew from the point you were born (and every point before and after) that you would go left what are the odds of choosing each direction? I'd say, regardless of how you might feel at the time, the odds are 0% for turning right, 0% for going forward, and 100% for turning left. Thus, regardless of whether you think you have a choice, the fact that God knew what "choice" you would make effectively removes the choice from your hands.
As a note, I don't believe in God, but I, too, do not believe in free will. I think it's a necessary illusion, but an illusion nevertheless.