Huge Family--Who are the Heirs, Do I really have to name/find them all?

My aunt recently died with a will naming me as PR and sole beneficiary of her estate (essentially her house). Her son and parents are deceased and most of her siblings are deceased. She had 11 siblings all of whom had multiple children (some of whom are now dead and leave children) and many of whom live out of the country and did not keep in touch. I understand I may need to name the "heirs" for the Petition to open the probate and will also need to send notices at some point. Are my aunt's nieces and nephews and great nieces and nephews considered heirs? I'm afraid there are likely close to 100 heirs if that is the case and it seems like a crazy amount of work to try to locate all of these people. Also, would a deceased step sons children count as heirs? Thanks!!