Next year she and my father will celebrate 45 years together, and since they only had a small civil wedding, I though it would be nice to give them an anniversary party including renewal of their wedding vows.... Also my Dad is an unbeliver although he has been very supportive of my mother's beliefs and supports her pioneer efforts financially. Since they are "unevenly yolked" would this make a difference?
Since your Dad is an unbeliever, a ceremony like this would not be permitted at a Kingdom Hall.
Since your Mom is a JW, she is forbidden to have the ceremony in a church of Christendom.
So they may be back to Square One, having a civil servant preside with a (hopefully) larger gathering in a non-religious setting like a private home or a rented meeting (not Kingdom) hall.
Oh, and don't forget - that rented hall better not be associated with Christendom either! Maybe they can rent a room at the United Nations?
It may be that your mother could find a kindly elder to provide the Watchtower advertisement ceremony, IF his Bible-Trained? conscience can handle the riptide internal conflict and self-doubt that has been hammered into him.
Some JWs may even object to the idea, claiming that a vow made before the Eternal Jehovah does not need to be renewed, because Christians let their "Yes" mean "Yes," and their "No" mean "No," as Mulan pointed out above.
What WOULD be highly irregular, in my opinion, is if the whole thing came off with no friction from anywhere.
Keep us informed, OK?