You don't have to arrange it, per se. When it comes time to settle the bill, the server will deduct the $50/each (if ordering off the menu), or there will be no charge if ordering prix fixe. Of course, alcohol is charged. I also add a tip commensurate to the entire bill, regardless if it was covered or not.
This process is the same for dinner or brunch. Usually it's applied to the first meal attended (if you're doing multiple Palo visits on a cruise), but if you'd like to save it for the next, just tell your server before tallying up the bill.