QM2 probably does not get as many teens as your first cruise, but if it is during the summer I am sure there will be some.
The ship just plain has great activities. like Drama classes, computer classes, astronomy classes, ship tours, etc. But they are given to everyone.
I really don't see much about the ships as far as catering to children goes.
If keeping your kids happy is a real concern, I would consider Carnival, Royal Caribbean, NCL or a larger cruise line.