The current plan (subject to change, of course
is to have a "rave"-like dance one night, and the masquerade followed by a "rave"-like dance another night.
As for the sleepover part of your plans, please keep in mind that the con closes at 2am, and that includes panel rooms. If you are planning to make this event a panel and having it in one of the panel rooms, you will need to be out of that room at 2am (you can always move to a private room). Unless the plan is to have it in someone's room anyway, in which case, nevermind.