What are the requirements ?  Must they be potty trained, in possession of present certain vaccination certificates or meet certain age requirements ?

Do they provide supervised play areas ?

What is the caregiver to child ratio ?

Are the personnel properly qualified and trained ?

Have criminal and other background checks been done on the staff ?

Is someone in attendence trained to perform CPR ?

How thoroughly are they insured ?

What security is in place when children are picked up at the center ?

What are the hours and cost, and are there any restrictions for this service ?

If  bunk beds are in use, do they have guardrails on them ?

Do they provide babysitting services ?

What are the hours, costs and restrictions ?

It really depends on how many there are in your family.  Also the ages and size of the people.  Ships are designed with two person cabins that can accommodate a 3^rd and 4^th person, if needed.  Check the square footage of the cabin to see if you want to squeeze everyone into that amount of space.  Regardless of the number of people in the cabin, you’ll still only have one small bathroom to share.

Before leaving for the cruise, check the line’s web page for its menus.

Determine whether they serve items that your child will like.

Does the ship have kid's menus available at every meal ?

If you are bringing an infant, remember to pack plenty of formula

What time do you and your kids normally eat ? Choose a meal seating close to the time that you would usually eat at home.  Check to see what time activities are scheduled for kids and schedule around them if possible.  Early seating is usually best for families.  A late seating might cut down on the evening activities for the kids.

Check well in advance regarding the cruise line’s minimum age requirements.  Don't be disappointed. 

Remember to pack a good supply of diapers and formula.

Even though they are difficult to use on a ship, strollers can come in handy and will be needed on shore excursions.

Bring a baby pack for both on-land and at sea.

Find out if rental cribs are available for the cabins or if they are provided free. 

They will need the same documentation that you are required to have.  If a passport or visa is necessary for you, they'll need one too.

When traveling out of the country with only one parent, written permission from the other parent is needed to verify that the child may leave.  A notarized statement from the absent parent is normally sufficient,  but check with the individual line for their policy.