Talking to the ex


So my boyfriend has two children from a previous relationship. He told his ex this past we are expecting for March and she was upset which is totally understandable, she thinks we will forget about the other children. That is not the case at all. My boyfriends mother thinks I should go for coffee or something to reassure her. Not that I’m against doing that I just feel like I haven’t had anything to do with her up to this point and I’m not really sure what to say... anyone been through this type of situation with any insight?