Hi Mike,
We are on the same cruise...my DD is also 12 but will celebrate her 13th on board on the 25th.
I've cruised multiple times with my DD (both alone and with my ex) and we always have a blast. Like someone said, Disney is very special and they specialize to have fun activities for kids but don't forget us grownups in the process.
Perhaps we can get our DD's together as it's always easier when they have someone their own age to 'hang aroud with'...