Narcissa’s smile was fake, because Sirius and Andromeda even though they were disowned came to visit and pay respect towards their grandfather. As head, she had to lead the funeral and make the speech. Narcissa said to Akira that he shouldn’t visit the funeral since he wasn’t safe here. She already told her family that Akira couldn’t come due to the risk he was in, if Albus found out. Her family was understanding it and told her that Akira didn’t have to visit the funeral since he was a bit too young too, but he still sent some flowers and gifts for the deceased, in order to pay respect for the dead.