Cohall

Zainman, someone had posted awhile back that they were able to grab 3 or 4 business seats on a single flight, so it's certainly possible.

I wouldn't book 2 hoping that 2 more come available later. Seems too risky for me. If you can swing it, I'd try and grab the 2 F and the 2 J seats on the same flight. More miles, obviously, but guaranteed you'll all be together.

Alternatively, you good book 2 J and 2 Y, and hope that 2 more J eventually open up for those you booked in Y.

Either way, good luck!