Honestly, I had been wondering for years why there was not space to include full names.
I received the email the other day and note (as did others) that at this time one does not have the ability to change this on their own. perhaps, in the near future this will be possible.
One quick call to NCL this has been taken care of. Don't forget your spouses, children, other traveling partners.
As a couple of others have noted, I login and see my full name but the initial reservation information does not. The E-docs show both of our full names and those are the important docs!