Hello CNR, and welcome to Cruise-Chat; there are four main dining rooms; one for Traditional First and Second Seating and three for Anytime. You can change from Traditional to Anytime once onboard, but not the other way around. Anytime has become much more popular than Traditional; hence, the three dining rooms devoted to it. But this means there is always a waitlist for Traditional, especially First Seating.
As to which is better, you will find as many opinions on that as there are members here. I prefer Traditional Second Seating; I love the quiet late afternoon hours around the pools while so many are getting ready for dinner. And I never have to worry about rushing back from a port or a shore excursion for First Seating. I also like having the same waiter and tablemates every night. There is a bonding that you don't get when you dine with different people every night. And Second Seating has always seemed less rushed, more relaxed. Everyone at First Seating knows the room has to be cleared and reset for the next seating.
But I have done Anytime and enjoy that too. If you are willing to share a table you usually can go right in. People that have to wait usually have requested a particular size table and one is not always immediately available. And Anytime gives you much more flexifility; you dine when and with whom you wish.
With a young daughter, you may wish to choose Traditional First Seating or Anytime. Also, people that really enjoy the night-life like to dine earlier.
My suggestion would be to choose Traditional First Seating; then if it dosen't feel right for you, you can move to Anytime.
Eaither way, what a wonderful way to spend the Holidays. Have a great cruise.