I am so glad to hear that you have little ones going. Our youngest will be 1 when we cruise. If you have any tips from your last cruise on taking one that young please let me know!
I sure do!
My husband surprised me with our last cruise as a Christmas gift and I was SO mad at him. I felt like my son (at the time of the cruise 11 months) was too young to take on a cruise and that it would be more of a hassle than anything enjoyable. I was COMPLETELY wrong!
I tend to be one of those over packed, over organized, super neat freak/germaphobe type of people. I blame my mom completely for this! haha I did find that it came in handy with the cruise. So here is my list of tips:
1) Bring an over the door shoe hanger! This was a lifesaver. My DH thought it was so ridiculous until we got on the ship. Then he was singing my praises. All toiletries, sunscreen, brushes, jewelry. . . EVERYTHING can be organized out into it. Just buy a cheap one with CLEAR pockets.
2) Zip lock bags. The uses for these are numerous and you will be glad you have some on hand.
3) Back pack. Don't mess with a diaper bag. We fit everything we needed in a back pack and it leaves your hands free.
4) Ask your stateroom host/hostess for a diaper genie. They have them available. The trick is knowing to ask. They change it out daily for you when they clean your room. FABULOUS!
5) You can also request a playard (portacrib/pack-n-play). This is where my germaphobe-ness comes into play! I have a playard cover from Coverplay and brought my own sheets to use as well. It fit in the room perfectly. They will set it up and tear it down for you everyday. We chose just to leave it up because naps and it really wasn't in the way for us.
6) Strollers. They have strollers available for rent on the ship. Basically they charge your KTTW card $200 and then when you return the stroller its wiped off. We never used the strollers because we chose to carry our son in a carrier harness. Daddy carried him back pack style and I carried the back pack and we were great. However, this next time around strollers will probably be necessary for our group so we will probably go with this to save space and the hassle of strollers in airports.
7) Snacks. Make sure to bring snack favorites with you because you will not find them on the ship. You can snag boxes of cereal from the buffet for little snacks too.
8) Sunscreen stick and/or spray can. Quick re-application for wiggly ones when you are out and about. The stick fits in your pocket too!
9) Don't overpack clothes. This tends to be one of my bad habits but I did well keeping the clothing minimal. Bring some Tide tablets and a couple of dryer sheets in the event that you run out of clothes and need to do laundry. Deck 6 and 7 have laundry rooms. And don't forget to bring a mesh laundry bag for dirty items. Keeps everything tucked away neatly in the closet.
10) If you are bringing bottles or sippy cups remember to bring a sponge/bottle brush and dish soap.
11) Magnet clips for your door. I would hang the navigator for the day on the door along with movie showtimes and the cruise overview. Very easy to see and access without cluttering the rest of the room. I also had a folder with clear plastic inserts to keep receipts, navigators, online ticket info for excursions, etc.
12) Don't be afraid to ask. The cast members are SO helpful and friendly.
And last but not least. . . ENJOY YOURSELVES!

Hope that helps!