I have a very large family (approx 100) so space for friends and extras is unfortunately limited. We have budgeted for approx 150 guests. We understand the etiquette of inviting the plus 1 for those married, engaged, or in serious long term relationships, we have budgeted for that. However there are several friends and family members that do not fit into that category. What is the proper way to make sure they don't bring a plus 1?