I just completed the outbound journey and it all went very smooth. The check in was without any problem whatsoever and they had actually blocked two seats at the front in the A350-9 with the super diamond seats if we wanted to have those seats with a bassinet. We ended up changing to those seats.
Our child fitted in it but the only downside is if there is the slightest turbulence they make you pick the baby up until the fasten seat belt sign is off again. So it worked better for us to just let him sleep next to us instead.
So nothing to worry about and enjoy your flights!