I agree with Logan. As cool as it would be for JFK or Princess Diana to drop by, I would invite the following:

My grandfather--Bruno Vavala--he was a great man, and my husband never met him, I miss him

My husband's father--Jack Morrison--I never got to meet him, I hear such wonderful stories about him, I would love to have a conversation with him

My husband's grandfather--Ed Braden--fascinating man, who I also didn't meet, he had planes and was very into aviation, I just hear such wonderful stories

My maternal grandmother--She died when my mom was very young, I would just love to meet her

My stepmother's father---he died when she was young, and I hear such wonderful stories about him from her and her siblings and her mom