Terrific response Margie in Forest Hills.   That's what makes these stories so fascinating --they BEG questions, and reveal new facets.  

God walking in the evening breeze reminds me of the Father looking for the Prodigal to come home.  In that parable, Jesus tells us what Adam and Eve SHOULD have done, and how God would have come running to embrace them -had they chosen to ask for forgiveness rather than cast blame.

Was it "fair" of God to lie about the repercussions of eating the fruit (or was it a lie --death of innocence, etc.)  ?  Would the same choices have been made if God had been more straightforward?

"death of innocence" is a great way to put it. Would the prodigal son have listened to a more straightforward warning? Prodigally not.

Was the choice to eat the fruit really a sin? 

The choice wasn't a sin. Choosing to go against God's rule was the sin. Was it wrong for the prodigal to ask for his father's inheritance? No. What was wrong was how he wasted it.

you can argue that God set Adam and Eve up for failure. 

You sure can, and it been a theological paradox for ages, ...the necessity of sin to demonstrate Grace. The requirement of failure and struggle in order to learn and grow.   Did the Father set the Prodigal up for failure by giving him the inheritance, knowing it would be the "death" of him?   Perhaps "innocence" needs to die, so that the Prodigal can learn what they have gained.

these would be concepts I would raise with our teens and not the younger students

Absolutely. We know others will raise these questions in an effort to discredit narrow answers. We need to teach our prodigal kids that God loves questions, and that our salvation is not dependent on the prodigal getting the answers right.