I would have thought 21 was the minimum age, however, I don't know whether RCI for this purpose considers Panama North or South America. I found this
on their website, but they don't say anything about cruises originating from Central America, which personally is what I would consider Panama.
You may want to call RCI to clarify this, or maybe another member can answer it better.
2007 - Majesty of the Seas
2009 - Enchantment of the Seas
2010 - Freedom of the Seas