Your stbx has some weird ideas, but don't talk to your son about it (and she should not have told your son about it, either). He should not know anything about the procedures of the divorce.

She has to be there for the Sept 24 date or one of 2 things happens, either you get everything you want or she gets held in contempt. There's a third possibility, that she's asked to appear by telephone, which is done a lot, but it's weird. People who appear by phone tend to not make a very good impression unless it's ONLY a scheduling hearing. Anything else, and you need to be interestsed enough to bother to show up.