Some people seem a little confused about a few things:
1. NCL and NCLA (Hawaii - POA) DO NOT handle tipping in the same way.
NCL - "daily service charge" - $10 pp - ABSOLUTELY NO NEED to tip extra. The crew is NOT expecting you to tip extra. YOU DO NOT tip your servers at the end of a meal - certainly NOT in the dining rooms - although it's a nice gesture to add a few bucks to the bill in the "pay extra" restaurants.
NCLA - "resort fee" (that confuses everyone) NOT A TIP . The crew is expecting and hoping that you tip them.
2. Each person DOES not require a separate credit card but your sail and sign card does have to be backed by A credit card. My husband and I had our sail and sign cards backed by his AMEX. However when we cruised with a friend in 2003. Her S&S card was backed by HER credit card and our S&S cards were backed by my husbands.