I would be hesitant as the security wait times can be 1+ hrs but and in December often more. Though who know on your travel date which is too far out.

If you can be out of the airport quickly you can be in the city in 30 minutes. I'd visit Central Park (go skating), Rockefeller Center and/or Time Square (which most NYers hate but seems a must-do for kids.).

You'd have about 3 hours for this before you need to head back.