Manage costs of a bachelorette party

You're the maid of honor and it's up to you to plan the bachelorette party. You've got a great night planned, but you need help from the other women on covering the cost.  Not all of them are in town until the morning of, so you need an easy way to collect. Something that doesn't involve you paying up front and getting the money from them at a later date, because you know how that goes. And you need a head count of the ladies who can make it.