I haven't thought about this. However, there is no way I'm allowing my guests to invite more guests. My FI already invited more people than I want to be at my wedding! I would have to in a polite fashion tell my guests that they are not invited to the wedding, if they want to go to the resort at that time it's fine, but they would not be included on my guests list or be invited to anything related to the wedding. That may be harsh but it's my wedding and you have to remember that it's what you want, not what they want.