We went last October with our two 3 yr olds and we had a blast!!! We are planning going again this October.
The cruise ships usually have "kid" friendly onship groups that are age appropriate. It was neat for them to be able to play with others and learn different things. They gave us a pager and if we needed to be there, we got a page. We used it during the afternoon & evening and it was great. I will probably take advantage of it again and they can stay earlier if they want to. We still have them lay down for a rest, so that is why we didn't get them their until the afternoon, but they have things for the children all day long. They also have "after hours" for extra $ but it is well worth it if you hit a late night with DH!!!
I packed enough clothes for 5 days on the cruise, which included an extra outfit a day and we had plenty left over. They have limited space in the rooms, unless you get a BIG one, but it was our Christmas present from my parents, so I wasn't complaining.
They have the twin beds that pull down and they do have side rails, just make sure you tell your Room person...they will take care of you!!! They will give you and your children wrist bands for the "life boat" purposes, and the perk with having little ones, you get to sit in front of others! It was great being first to get in line for it and the first to leave. :)
You can always talk to your travel agent or call the cruise line if you have any other questions about things you need...espically if you have special needs.
Packing a backpack is a great idea, so you have things handy when going on shore, or just around the ship. The umbrella stroller is also a good idea, but remember you have to lug it on & off the ship, on land it is fine, but if you have to go ashore, you will have to take it on and off the little boat that gets you there.
Bring lots of sunscreen, since it is hotter & sunnier than you think. You don't want burnt children. They do have a sick bay on board, but you don't want to ruin your cruise by spending the day there with a sick child or yourself from sun poisioning. YUCK!!!!
Hope that helps! ENJOY your family cruise and have a blast...you will want to go back again and again!!! :)
Blessed Momma to Ash & AJ ~ 4 yrs old