Halloween // help!

some family and I are going on a Disney cruise in October, it'll be over Halloween so it would be fun to have matching costumes! but it's actually so hard to think of a group set that would work... there's me, my boyfriend, my mom, my cousin, and her husband (all adults, 3 women 2 men). can anyone help with appropriate ideas? 😃 they don't REALLY have to be matching or Disney themed but it would be fun!