Don't mess with your tickets. It's always possible that it works, but much more likely that it does not and that something else gets loused up.
Best option is to wait until boarding and deal with this informally with the lead FA for the J cabin. Simply ask if it's OK for your wife to take your seat and be done with it.
On a US carrier, this would all be easy. Either your wife takes the F/J seat and tells the FA or you swap with your wife's seatmate and take a Y seat. Not on many non-US carriers.