Ok, so we just booked Athem of the Seas for April 17 sailing. It's April vacation week so Thrill Park passes are already sold out. I'm told to check in with the excursion desk when we get on board. Do they always open up some slots or will spots only become available if there are cancellations? Am doing a mother/daughter trip with my 13 year old and she is really looking forward to the water slides....