Just spoke to the nice lady at CX who allocated the seats for us. Although she did say that the increased baggage allowance would only apply to myself.

I also asked about interlining and she said its only possible with Dragon Air. Although she did say to call them back with any future booking reference from another airline and that they could "link" them. This apparently wouldn't allow the bag to be checked through but would make ground staff aware if there was a tight connection.