You didnt have luck getting them to deconstruct? I've used that one to move children a few times. Really hoping Toady hasn't broken that in 40_07 with a deconstruct labor.
Also didn't twig that you started both, you are really having a bad day.
Girlinhat had a few good suggestions, and is exactly the person who would know which ones work, having plumbed some...shall we say odd...depths in DF. Including several child research programs with heinousdwarfy ethics.
I would probably start with bedrooms, I do see children in bedrooms a LOT, since I dont assign rooms, just create them to be claimed by the next dwarf to sleep there, most of my kids have rooms and hang out there a lot. Build a wall in their room and try and get them to come deconstruct. As soon as the wall flashes you check 'u' to see who got the job and can it/re-designate if its not a child.
EDIT: ok, lets speed up the spiral then, wheres the biggest brawls? dining rooms, busy corridors, station the badass military there and some idiot will take a swing, once they get going though you may not be able to pull them in. Im not sure if they will react just at the sight of violence, a tantrum isnt a loyalty-cascade after all. This may leave you with more or less just your squad if it goes poorly, since it may not be the children who hit them first, but unhappy productive workers. Anyone punching a military dwarf is going to go down, just watch the miners. Once you thin the numbers it may become more managable.
Another idea is to set the military off-duty and try and get them to move some bodies if you got stuff piling up and creating Horrified loops, though the fighting will be scaring the civvies just as much.