The way I understand it is that there are 3 people travelling (ie 3 separate tickets)

If you are flying economy and your destination is JFK, then you are allowed 2 x 23kg each (total of 138kg) as you outlined in your post.

EK uses the "piece" concept when calculating baggage to and from the US. The details are here
http://www.emirates.com/sg/English/h...x?faqId=490107

Because you are travelling with an infant EK will grant you an additional 23kg. But the total dimension of the bag/item must not exceed 158cm (ie length+width+height) and the item you are describing is nearly double that at 317cm total. My suggestion is to split the stuff into 2 or 3 bags and then go online and pay for what you think will be the overage (as you do receive a 30% discount when paying online). You'll pay US$123 per additional piece if you prepay and if you do it at the airport - you'll end up paying US$175 per piece.

The challenge will be whether or not you can take the actual baby crib with you. You know for all the trouble and effort of lugging it all that way (and the cost to do so) you might be better off buying one in the US, where prices for that sort of stuff is very reasonable. Good luck.