Impossible to answer your question without knowing price difference and how much you can afford. For the same price/miles, 2 in J would probably be better.
However, the difference between Y and J is not as great as it would be if traveling without baby. Even in J, you are unlikely to have a good, easy flight: your job is to take care of a baby. Any in Y with 3 seats, you will have more space than you are used to. You will likely have an entire row of 3 seats, and the baby hardly takes up any room. Plus, you may be able to put the baby in its (his, her) car seat, the best possible place for it.
Using a car seat is actually the only safe way to fly with a baby. On a practical note, it's no fun being pinned under a sleeping baby, unable to go to the restroom or being able to eat or sleep comfortably, even if the seat is bigger.
A bassinet is no replacement for a car seat, in terms of safety or convenience. Many are too small even for a 6 monther and getting one is not guaranteed.
As a pp pointed out, the comforts and advantages of business are less a factor with a baby.
This is controversial to say but also, Y is more "baby friendly". As a Flight Attendant, I got more complaints about babies in business than in the back. But don't let this be a deal-breaker. It's still your right to fly in business with a baby!
So it seems like there's no consensus and it's a matter of personal preference? Thanks for no help My thought was that being able to have the baby sit in his car seat was a big plus. However, sitting in Y with no status isn't something to look forward to. I'm still undecided!
The three seats in J seem to be winning. That's definitely how I'd go...
The car seat is definitely a plus. If you go with two seats in business, be zen in the fact your child is not secure and make sure you both take turns with the baby!!! I have one of those husbands who will sit and let me do all the work (unless I insist) so it also depends on how hands-on both of you are.
Having the car seat meant I didn't have to hold the baby all the time, especially when s/he fell asleep.
Another vote here for 3 seats in Y. My tolerance for non-stop holding of a baby is only about 3 hours. As Eclipsepearl notes, handing off the baby to the father only works if the father is willing. Mine wasn't. Hopefully yours is if you decide to go for 2 seats in J.
Also vote for three in Y. That way you all have your own seats. There's really no benefit, IMO, in sitting in business/first for this flight. The FAs won't help you, you can't enjoy food or drink holding a baby.
I don't think status or no status makes any difference.