It is physically possible to rotate any of the seat pairs 180 degrees; that feature exists primarily so that if the car has to reverse direction somewhere where there is no wye or loop in the track, all of the seats can be reversed.
If a group of four could get the frontmost two rows of seats on one side of a car, it would be possible to rotate the frontmost row to face backwards without interfering with any of the other parties on the train. You do lose access to the tray tables when doing that. And it's best to not rotate the seats without the crew's approval.
I suspect you'd have an easier time getting that block of seats on a train that originates at NYP and not on a train coming from Springfield or Boston, but even then, there are no guarantees that you can get that block of seats, or that the crew will be willing to let you do that, especially with a party of three where doing that would prevent some single traveler from being able to use the last seat in that group of four and have access to the tray table. On the other hand, if the train is relatively empty and you can get that block of seats, it probably doesn't hurt to ask nicely if you're prepared for them to say no.
