P&O have good facilities for children and a supervised night nursery til 2am for under 5 year olds See http://www.pocruises.com/before-you-sail/faq-Families/Younger-Children.asp.
We took both our daughters on Pand O cruises when they were babies and 25 years later my elder daughter took her son to Norway at 10 months with Pand O. She said the staff were wonderful and he kept some of the elderly passengers entertained.Both my daughters have recently given birth (October)and have already booked with Pand O for next year.We are going with one of the families to Iceland and Norway. Just one or two points. Check your cabin for sound proofing . Not everyone wants to sleep next to young children who may cry in the night. Food is not usually a problem and the night nursery is good but you are ultimately responsible as a parent and you can't expect ship staff to take babies off your hands completely.Our girls grew up with cruising and thought Canberra was their second home!!Both their husbands have now got the cruising bug.
It is not right to take such a young baby on a cruise it could make them sick if the waters are rough, wake up and live in the real world, if you wanted to do cruising you should of thought of this before haing a baby.
I think on Princess Cruise ships babies have to be a year old before they are allowed to go.