What is the proper etiquette when writing wedding invitations when the father of the bride is deceased and the mother of the bride has not remarried? Would it be Mrs. John Doe or Mrs. Jane Doe or Ms. Jane Doe?

We have seen invitations worded with all of the choices that you listed.  However, after consulting with Carlson Craft (a large invitation printer), they advised us that the correct etiquette is to use Mrs. John Doe.  The sample they gave is "Mrs. William Lewis Baker requests the honour of your presence at the marriage of her daughter Barbara Ann"

Weddings are always a little tough when parents have passed on, and our hearts go out to everyone who faces this.  Best wishes.