I've been on two cruises.
Yeah, they were both Disney.. Land/Sea.
But take my word, Disney or not THEY ARE FUN.
You don't have to spend time on a beach, you can do shore excursions like parasailing, climbing water falls in Ochos Rios, water rafting and all sorts of neat stuff.
There's also teen clubs (it appears that
RCCL is better than Carnival for this) where you can meet other people etc.
It's more relaxed than Disney, but not as fun.
Ask you mother if she'd do this:
Go down early to Florida, before the cruise and spend a few days at Disney. Stay offsite at a cheap hotel, and do a couple days at Disney. The drive from Orlando to Cape Canaveral is about 45 minutes, so you'd have to rent a car.
Yes it'd be slightly more expensive, but it's a thought.
Remember. there's no icebergs in the Caribbean.