Thanks for the responses. So it was very nice of CX to offer one upgrade to me. This was within the constraints of what you say as my wife (emerald) was linked to infant and my son (sapphire) is only 4 yrs.
it worked out fine as I got the last row window seat in J and my family had bulkhead window and aisle in PEY. So there was just the curtain separating us and landing duties etc could be assisted with.
I feel that CX offering me the upgrade was a great gesture and much more than BA did in an overbooked DXB-LHR, where they just overlooked all of us presumably due to the infant in our booking.
PEY bookings to CX in future where possible!