Are you sure about wild animals not procreating? I swear I remember a herd of horses get trapped in a closed off construction site in one of my fortresses once, and at one point horse foals starting pouring out. Don't ask me what they ate in there.
Wild animals can breed, so long as they have the [PET] tag in their raws. Horses have the [PET] tag, so they can breed - even if they're wild horses. And only tame animals need to eat, so wild horses don't need to graze.
But on topic, I don't think intelligent tag or anything involving sentience has any effect on breeding, in fact I remember my last fortress having some tiger man cubs running around. They were tame however if that would indeed matter.
Minotaurs are semi megabeasts arent they? I don't know how that effects it.
Intelligence doesn't matter, since tame tigermen can breed. Being a semimegabeast might, I'm not sure.
I'm just afraid if I lock them in a room that they'll kill any child born since the child will be 'friendly'.
It shouldn't, since wild animals breed and don't kill their children. There is some weirdness with the offspring of invader mounts where they'll attack their children, but that shouldn't apply here.
In addition, what do the tags [BABY:1] and [CHILD:12] mean? Does that have to do with how long they are classed as children or the amount of children born?
It's the ages of transition. They'll be babies until they're 1 year old, then children till they're 12 years old.