Hi Karen 69er, welcome to Cruise-Chat! Congratulations on your up-coming cruise! I believe CruiseDad is correct, it is $10/pp per day. I know it sounds high, but it really isn't. It goes into a pool and people you don't even see, but do things for you, receive a share. There are pros and cons and many people think it should be included in your cruise fare. However, that would just raise the price of the cruise.
For example, we went behind the scenes on our Epic cruise. The laundry room was bustling with people we never saw on deck. 12 hour days for the staff. They were washing, drying, ironing, folding sheets, towels, pillow cases, napkins, etc. On top of that they take care of the crew's laundry as well as the passengers. Then we went to the garbage recycle area. The glass and plastic and cans are sorted by hand, then placed into the appropriate machines. And the list goes on and on, things you never even think of.
I totally agree with CruiseDad, you'll be amazed at the service. I'd go out walking at 5 am, there would be staff out washing every window, handrail, deck area, placing all the chairs out, filling and preparing all the self-service drink machines, yet smiling and greeting you when you walk by. NCL was $12/pp per day, but we ended up giving extra to our cabin steward and a couple of the bar tenders.
Just remember, it's always your option and you can adjust the tips at anytime by visiting Guest Services (the purser's desk).
Hope you and your family will have a marvelous cruise. I have a feeling you'll come back addicted like the rest of us