You should be able to select your seats FOC in Manage My Booking if you have an infant on the booking.

There are 3 bassinet positions in CW on the A380 - 10J & 14E on the main deck and 56B on the upper deck.

We found 14EF to be the best option when we travelled with our 11 month old on the A380 to IAD last year. The two middle seats make an enclosed area with direct aisle access. We were also lucky that there was no-one in 14D or 14G either way. Sitting next to each other, facing the same direction, with the bassinet directly in front of us both was definitely easier than it would have been in one of the side pairs facing opposite directions.

It's also near the two CW rear toilets on the main deck which is handy for nappy changes. We did find those toilets quite small and there isn't a lot of space for dealing with a baby. One advantage of the upper deck CW cabin is the massive toilets at the front.

We were concerned prior to the flight that there may not be enough bassinets / child seats (BA offer both, bassinets for the babies, seats for the slightly older infants - both go on the same fold down ledge in the bassinet position) as you can't reserve one before the flight. We asked for it as soon as we got on board but it wasn't a problem and there didn't seem to be any shortage at all.

We also found the crew were happy to offset our meals and allow one of us to eat first whilst the other looked after the baby which was really helpful.

Good luck with the flight.