Thanks adelee,
We have done so much research on taking a bub, but everyone has been so helpful! I can't PM due to post count though, but very much appreciate the offer.
Updates and more info that may help others:
1- Beware if you book a RTW in J on OW as if you have an internal sector (that starts and finishes in North America), that you will be getting a Y ticket (as they have two class flights F and Y 99% of the time), then you will get NO lounge access and NO baggage allowances! I am led to believe from research that you still have lounge access and baggage allowance if a Y segment as part of a transit that involves a long haul, though you will need to check individual circumstances.
2- AA has some trans-continental flights with J and also some shorter flights. Plus, be sure to check flight numbers of international flights (including other airlines) that continue through US cities (as they have J cabins usually).
We have just changed from SFO-LAX-YYZ in Y to SFO-JFK in J. Much more comfortable. Even if we added JFK-YYZ to this, we would have been charged baggage and sat in Y for that sector. Almost as cheap to get a J seat with cash. We were planning a side trip to the big apple anyway, so works a treat!