It would depend on the age of the kids in your SS class. If they are 10 or older, you can definitely go into more detail. Younger... probably not. Depends on the kids.
But you have at least one kid who is thinking! Thats great.
The first sin was not eating the fruit. That was the first law that man broke. But sin started as a seed within the heart... "you will be like God" was enticing, and appealed to their PRIDE. Eve sinned before she ate the fruit. Eating the fruit was the manifestation of the sin of pride. It was the acting out of it.
It can be a good thing to point out, especially to kids old enough to understand this. What that will do is cause them to look deeper within their own hearts when they do sin. It will go a long way in showing them how wretched and evil their own hearts are, and why they need a Saviour.
Then someday when Ray Comfort comes up to them with a camera and a microphone and asks them if they are a "good person"... the kid and rightly answer "No! I'm not!"
Krispy