A buddy had to use his wife's AC credit so he ended up booking a RT flight in Y to NRT (under his wife's name). He also decided to use some of his AP to book a RT flight in J to NRT, same itinerary as the one in Y and under his name.

Now, there's an infant involved, who will be 6 months when the trip occurs. He planned to put his wife and kid in J while he sits in Y. So he's just gonna tell the AC agent about swapping the seats with his wife.

I am assuming that as soon as the kid's name is in the wife's itinerary, AC will accommodate her by allocating her a bulkhead seat with a bassinet in Y?

I have no seen it myself but can you get a bassinet in J?

Any other pre-planning that should be done?

YEG-YVR-NRT-YVR-YEG is the itinerary.