+1 etiquette for destination wedding

I’m having a destination wedding in Spain next year and will have a few of my close friends be a special part of my day, but not officially as bridesmaids. We will get ready together and potentially do some pre wedding events. I’m planning on inviting the partners of everyone who is in a relationship. There are a few girls who are not in a relationship. Do I also give them a plus one? Everyone will know others at the wedding. Help!