Also consider the length of the cruise and what time of year you want to go, as well as the itinerary. You can have a spring or fall 7-night cruise for the price of a summertime 4-nighter. The shorter cruises also tend to have the older ships with lesser kid's facilities, although there are exceptions such as the Liberty Of The Seas for Royal Caribbean. That ship has a lot of stuff for kids. RCI also has the Royal Tots program on their larger ships which would give your youngest a limited activity program, plus they offer a nursery for $8 an hour in the evenings. The 5-year old would be in the Aquanauts youth program.