Who determines what the theme nights are and on what nights they will be? Also are these binding to all guests at the resort?
Usually there are set theme nights that are set up by the resort itself. Then if there are large groups of people who are going at a certain time they usually set up their own theme nights for the nights they will be there. Usually whatever month you are going there will be a thread or sticky(roll call for that month generally at the top of the page) where theme nights are discussed amoungst those going those weeks and it is mutually decided what everyone wants.
The resort has white night, pool party and Lingerie night....I believe. Participate as much as you like or as little as you like. For us we like to do a few of the nights and have for the most part just done the ones that the resort does. Last year I brought the glow sticks to add to the pool party. You won't be alone for sure but each week is different depending on who is there. Have a great time!
Like they said, the hotel does the White night and the Lingerie night the rest are planned by the guests. Participation is optional but sometimes (hell all the time) really fun! Jamie
The only thing you are absolutely required to dress appropriately for is Thursday Lingerie Casino night. Other than that, all events are completely up to you whether or not you want to participate and at what level.