Wow. I haven't had this discussion in years. I grew up super religious (even was ordained to the priesthood in my early twenties), so this is one I had with many people years ago. I am not so religious anymore, and am more open minded now that I am middle aged but just for the sake of discussion here goes....
If God is omniscient it does not mean there is no free will. First of all it is never "free" - as any act of expressing your will carries consequences - you will either pay or receive benefits because of your actions.But just because God knows the future it does not mean he caused the future.
If God is truly our Father - or our Parent - or Legal Gaurdian - he has much more knowledge than me.
If I, as a earthly father, am watching my child do something - I can often predict the outcome. Even with my limited knowledge. I can tell my son is going to fall from a tree, or that he has impressed a girl, or is going to slip and cut himself, or is going the score the basket during a basketball game. I can tell if a 18 month old is going to drench himself in soda if he lifts the glass too high-although they did not foresee that. Kids sometimes think parents have eyes in the back of their heads because they "know" what is happening - buts its just because parents have been around a bit.
Sometimes I can tell there is going to be a bad consequence to an action for a child, but still let them do it so they will learn something (of course not if it was truly dangerous to them). Sometimes I let them learn that doing something is wrong or doing it the wrong way or at the wrong time is not good - so that they truly learn the lesson.
If God is perfect - he is perfect in 7 traits : knowledge, love, truth, power, justice, mercy and wisdom. He may have power to make anything happen - and could make life an easy perfect fun journey for us - but that would contradict perfect wisdom - because a child has to be allowed to walk on their own, even though it means falling down many times.
If he is our Father he wants us to grow up and become stronger - more like him ( "Be ye therefore perfect even as your Father which is in Heaven is perfect" - Matthew 5:48. It is an actual commandment to eventually become fully developed - a commandment just like "Thou shalt not steal" - however we choose through our "free will" whether to obey the commandment or not). To become stronger we have to be allowed to do it on our own. You can't get stronger by letting someone else lift your weights at the gym for you.
God is wise enough to let us go our own way, make our own mistakes, express our "will" - and either pay the bill or earn the paycheck. As a Christian I was also taught that he provides a way to help pay our spiritual (and some physical debts) that we cannot pay ourselves, through the grace of Jesus Christ, after doing all that we can do.
Wow. That almost brought tears to my eyes - haven't felt that for many years.