Royal Caribbean has a great teen/youth program. My 10 year old has been on 15 cruises and she rates RCI tops!
Radiance is a nice ship with plenty of outdoor activities even if it's too cool to swim -- basket ball court, mini golf course, rock wall. Your teens are a great age to enjoy such activities. Tell them to give the teen programs a chance too, but don't count on your younger one being in the older teen group. You can ask the counselors when you get on board but it is often not allowed. They would be more apt to have an older child move to a younger age group than vice versa.
Luisa Frey Gaynor
Family Cruise Editor