This depends on how you booked - if you book through the Hilton site then no additional charge for Children is added so you will need to pay it at the resort (including on points bookings). If you book through the Playa website, the extra is added to the total cash value so there will be no extra to pay later. You can tell this because taking the child off the dummy booking reduces the total by the $95. Both work out the same (or within a few dollars) once you've included the children.