Thanksgiving Dinner Dilemma

Leo and Rebecca Buzz Question; My WIFE has invited both of her parents to Thanksgiving Dinner this Thursday...they have been divorced for 15 years and SHE's NOT TOLD EITHER OF THEM THAT THE OTHER IS COMING TO DINNER. I told her she needs to give them a heads up but she says if she does they wont come. Should we expect DRAMA this Thanksgiving?? Should I try to advert it?