I suppose this decision depends on why you're inviting a fan guest to begin with. If it's to honor someone who has made a contribution to fandom, whether local or on a national or international scale, then imho that person should feature in all of your publicity just like the other guests. Being named in that way is one of the ways you honor the person.

Your publicity is certainly intended to get people to come to the convention but I don't think that means necessarily that you shill the professional writers and eliminate the fan guest from your list because outsiders might not know who they are or what a fan guest is. Instead, my feeling is that your publicity should be including all the things that make your convention what it is, including honoring people within the community.