EWR is delayed
JFK is delayed
LGA is delayed
SWF and HPN are delayed because of incoming flights from JFK/EWR/LGA
The closest airport that B6 flies to with no delays would be...uhh...nowhere
In reality, the whole NE is delayed and the best bet for minimal delays would be early morning flights and loads of luck
I can't see why JFK would be any better than EWR for delays.
If your parents are really concerned about delays they should drive to PBI, drats, delays on I95