I have traveled recently a number of time across the Pacific. I found JFK to be the most confusing, and difficult place to get around. On my last flight from Toronto to JFK, I had to run (literally) to the next terminal and no one was helping me to see if I would be able to make the flight. The signs are confusing. Be prepared for people to be impatient with you and not give you good directions. I have flown domestically and internationally from JFK and I ALWAYS have some sort of problem there. They often have long delays and I have missed multiple flights from taxi-ing on the runway for a couple hours. Now I try to use other airports for connections because its just too difficult.
Airports in Tokyo, Seoul, Detroit, even Toronto are easier than JFK. I think my main problem was with the "service" I got from various people working there. They stand around, making it look like you can ask them something and then they act like they dont have time for you, or that you are interrupting them. There was one lady who was very patient and helpful when I kept getting lost.
As far as I know every time I enter JFK I am forced to collect and then recheck my bags for my next flight. I have always had to re-do security in JFK.
If you do miss your flight, they will likely book you on another flight even before you land. Keep asking the flight attendants. If you arrive in JFK early enough in the day you may get another flight out that day, otherwise you will be forced to pay part of the hotel bill to stay overnight (JFK does have one terminal that is open 24hrs and I stayed there for 16 hrs before, but that would be far too difficult with a child). They have a service available to checking your bags at the airport, for quite a decent fee (read: more than I thought it should be), so that you dont have to carry your bags around.
JFK Connections