There are basically two classes of Motorola radios.. the consumer class and the "business" class mentioned which really means that you would need a FCC liscense to use them. These radios have a much further range than the consumer radios. (And you should not be able to buy them without a liscense.) But there are consumer class radios that have really good range (1 mile or more) and they work really well. Be sure to get a model that has many channels you can use so that you can swithc around and find an unused channel. Most of the Motorola radios offer at least 7 channels each with multiple sub channels.
And bring extra batteries. If the kids leave them on, they can drain down in a couples of days.
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise
NCL Dream October 2006, RCCL Mariner OTS June 2007