Sorry did someone summon me?
Let's get to it, then. Is your problem with INFANTS or with CHILDREN? Infants are attached to their mothers, children will follow their mothers.
INFANTS - You need to either separate them, or kill them while the mother holds them. For quick killing, danger rooms are fine. A few pumps of a spike will do it. For separation, water would be my best bet. Basically if you send the mother through a waterfall type area, the flow of water will push the baby off them and preferably down a death hole. BONUS POINTS if the death hole is actually just the dining hall. Witnessing death will get them hardened to disappointment, and make them virtually immune to tantrums.
CHILDREN - These are easier to handle. In my experience with DF2012 and attempting to weaponize children... yes, 'that' thread... I found interesting things. Children will only slightly obey burrows. They will always obey an alert burrow, but a personal burrow they will only stay inside - they will not go to it easily. If you set an area as a burrow, and the child accidentally walks into it, they will stay there. Children will also claim and stand in their bedrooms.
For mass slaughter, I would suggest making a smallish room, layered in upright spikes, and set it as a personal burrow for all children, and ALSO as an alert burrow. Call the alert, all dwarves go to the spike room. Cancel the alert, all adults leave, and all/most children stay in the spike room, because it's their burrow. Once safe, lock the door and pump spikes.
For individual death, assign bedrooms to children, and once they're inside, have a mason seal them in, so that you can add turkey to the room let them starve or add lions or drown them or whatever. You may even just build small gazeebos outside, without protective walls, so that goblin snatchers or ambushers wander by and kill the children for you.
As far as avoiding tantrum spirals goes, then you want to put everyone in an unused military squad with a uniform of just a helmet, allow parties, and make sure the bodies aren't found. Cave-ins help to demolish bodies, as do bridges.