The spoiler doesn't really change anything because Luffy/Nami can't do anything to progress the plot. One of the children going to taunt Luffy makes sense. Only thing is that the son/daughter has to be acting independently since Big Mom so far has kept her word. The child preparing an attack would explain Luffy's response and Nami's reaction. As for the tooth, it makes sense since it a nice visual impact on the clash with Sanji. I am torn because Luffy smiling is like his signature, so the missing tooth seems out of place. Luffy heals miraculously when he eats meat (getting impaled by Crocodile and having the wounds close after eating meat), so I agree with @Marco Polo that him growing it back after eating would seem likely.