We recently sailed with NCL. There were three of us in the same room. We each had our own card (separate credit cards). The only problem we had, was my mother and I have the same last name and there were some charges on the wrong card. This was easily taken care of on the last day. Have a great time.
Yes, everyone will have their own S&S card and you can each have your seperate charges placed against your own account. Just tell the person that checks you in that you each wish a seperate account.