Thanks to all your advices and also to the welcome.
Actually I was thinking about something within the airport, because I don't want to risk to lose the connection.
I have been a C/A for some years when younger and I remember how kids can be...
I tried since the very beginning to teach mine how to behave properly, ESPECIALLY ON BOARD. Respect, first of all, and they know that.
So they are pretty good usually, and I've been taking them around many times, even if not so far as a 24 hours flight! But... usually a little transit is well manageable, and we've had many before.
I always try to have short transits, up to 3 hours.
Unfortunately this time Delta has changed our schedule, so I have to face this long transit.
I was looking for a play area like those we met at Atlanta airport, those were crowded but so useful, they could so some physical activity and then get on board ready for a quiet flight.
It seemed strange to me that a HUGE apt like JFK doesn't offer anything like that. I was searching through all the website (JFK) and there's nothing. NOTHING AT ALL. Isn't it strange? there are so many children travelling nowaday!
Anyway, I will contact delta and ask for their paid-for lounge. But... any idea is more than welcome. the tour is good too, I will look for it. again, thank to all of you. I am really appreciating your support and this forum is just... great.
F.