I have a large family who likes to cruise, just not as often as I do.
I book all of our cruises / drink packages / dining packages / shore excursions with my credit card and share the benefits they earn for me.
Make the card work for you!
Our group of 7 (5 cabins) were on the same cruise. We all had the UDP and the beverage package. Every bar and restaurant we visited was excellent. Really good food and service.
Getting off this morning was a mess, however.
In the past you could go to Guest Services and get a new ID on your 21st birthday.
They usually don't acknowledge other birthdays - going from one children's group to another, however.