Sorry I took so long to reply, I don't know why I miss my Nostr notifications so often.
You're right. Children are plenty capable of feeling empathy and sympathy for animals. When children learn about what it takes to get meat, they often do ask "why."
But my mom finds that all it takes to get them to accept the treatment of animals is to say that it's how we get our meat, and to ask them what else we could possibly do. That tends to address their concerns pretty well.