To think that God didn't know what would happen in the Garden is to acknowledge that He is not omniscient. In fact, the entire Garden story has all the elements of a setup. In fact, God intended for Adam and Eve to fall; otherwise, as you note, He would not have placed two innocents in a setting with the Adversary. The question is why? Why would God do it? What possibly could be His motive for having Adam and Eve fall?
For one thing, they could not fully gain a knowledge of good or evil without partaking of the fruit. This knowledge, as well as mortality, was essential to our growth. Only through the process of gaining mortality, and the knowledge of good and evil, could we experience pain, sorrow and hardships -- things that were vital to our becoming like Him. At the same time, we needed a Redeemer to pull the plug and ensure that we had a way back. In short, it was part of the Divine Plan. Read Timothy Ware's The Orthodox Way, for a better understanding of how this all works together to bring us to salvation.
The Jehovah's Witnesses see the sin in the Garden as a horrible mistake, and after Jehovah-God sent Michael the Archangel to die on the cross, mankind will be restored to a garden setting, where people will just sit around playing musical instruments, gathering fruit and tending to the garden and to animals. Strange that their publications don't show anyone naked, but if they're correct (and I don't believe they are), why would anyone need clothing? We'll be pure-minded and go back to what Jehovah-God had in mind for us. Just sitting around all day doing nothing constructive at all -- divine pets.
I believe, as Timothy Ware argues, that the divine plan was for God to become as we are so that we could become as He is. John said it doth not yet appear what we shall be, but that when we finally see God, we shall be like Him, for we shall see him as He is. And as Jesus was resurrected physically, with a spiritual body (animated by spirit, not blood). In short, there will be no heavenly class and earthly class people, for all will have physical resurrections, and all (including Adam and Eve) will find that they, through the Atonement, have become far superior to what they could have possibly achieved, or become, in the Garden. It's just another example of the JWs having a narrow minded theology.