Knowing and decreeing are just different things, by definition.

If we have free will, then God knowing that we will choose to sin is not the same thing as God causing us to sin.

I'm not sure what you mean by "mutually exclusive". All I'm saying is that foreordaining and foreknowledge are different things.

God foreordains because he foreknows. For example, he can give special blessings to believers based on his foreknowledge of their decisions to accept Christ.

But I think Calvinism teaches that God foreknows, because he has foreordained everything. So the two are conflated.

They aren't mutually exclusive; I'm arguing that foreknowledge is not an effect of foreordaining - the idea is kind of odd when you think about it - why say God can foreknow things, if it's assumed he caused them to happen in the first place?

If we go to Scripture, it's clear that foreknowledge and predestination are different.

"For those God foreknew he also predestined to be conformed to the likeness of his Son, that he might be the firstborn among many brothers." Romans 8:29

To me this says foreknowledge and predestination are not the same thing. It also says that one follows another: predestination is based on God's foreknowledge. If God foreordained everything, then foreknowledge would actually make no sense: God foreknew what he had already predestined?