Hi PC Guy,
In 2004 my wife and I cruised with our son and daughter and their spouses and our 7 month old grandchild. It really went well, the little guy loved all the attention. My daughter or my wife had to miss a few things while staying in the cabin with the baby. There were a couple times when my daughter left with him during dinner because he was crying but most of the girls who worked in the dining room made a big deal over him.
Make sure you have documentation to proove the baby is yours, certified copy of a birth certificate is probably sufficient but check to see what is required.
You will need to bring diapers and food and the cruise line should be notified of your need for a crib. Breakfast in the buffet should be okay with scrambled eggs, pancakes or waffles and fruit if the baby is up to that. They will give you boiling water in a pot to warm up milk or formula if you request it.
That is about all this grandpa has to tell you.