Susan,
I have to agree with you in miracle of turning water into wine that is was not simply grape juice but was in fact wine. The reason for this is found in John 2:8 NIV below. If it were simply juice then there is no meaning to the comment from the master of the banquet. I think he is saying here too much to drink impairs their ability to distinguish between good wine and bad wine from the alcohol content.
8 Then he told them, “Now draw some out and take it to the master of the banquet.”
They did so, 9 and the master of the banquet tasted the water that had been turned into wine. He did not realize where it had come from, though the servants who had drawn the water knew. Then he called the bridegroom aside 10 and said, “Everyone brings out the choice wine first and then the cheaper wine after the guests have had too much to drink; but you have saved the best till now.”