One of the easiest ways to avoid any such worries is to theme your party. By making your party a fancy dress one people will often feel far more comfortable as they will have a persona they can hide behind, making them far more likely to be outgoing and in turn far less shy even if they have opted for a very sexy fancy dress costume.
Furthermore, by choosing to have a fancy dress party you are far less likely to find that people let you down at the last minute. Once people have bought their cheap adult fancy dress costumes online they will be ready and excited for the party and will do their best to avoid anything else cropping up, not least to ensure that the money spent on a costume doesn’t go to waste.
At fancy dress parties, people will be far more open to chatting with strangers and will feel far less self-conscious. As such, not only will your guests have more fun, but you will be able to simply enjoy your night as opposed to worrying about everyone else.