is a link to the Soda Program on NCL's Web site. As of now, it's $4.00 per day for kids 12 and younger, and $6.25 per day for pax 13 and over, plus 15% for gratuity on each. By "per day," they mean the number of days of the cruise. So, for a 7-night cruise, that would come to about $50 (plus whatever taxes they assess) for an adult.
I haven't been on this itinerary, although it looks great. Are there any ports that interest you more than others?