You're forgetting 3 things.
1) She lives in a Mideval Era. Where commoner children worked from sun up till sun down, from the time they could walk.
2) All the work they're doing is substance farming for themselves, so what they farm, is what they eat. It's not like she's making any money at all from them. If anything two chapters ago, it was shown that she's actually losing so much money, that the village chief needs to pay out of pocket to support the kiddos.
and
3) It's not child labor, like you're talking about. Sure kids are working for a living. But all that work is purely for their own survival and all they do is going onto their own plates. Since there are no adults outside of the village chief until this chapter. Which makes sense since it's a stigmatized race that humans go out of there way to condemn and treat more worse than black people in 1700's USA.
So without adult supervision, outside the chief. No support networks for children, outside what the MC can give personally when she's there (which is rarely). And without a massive infrastructure, since it's a mideval ghost town, that was falling apart at the seems when the MC got it. They got to fend for themselves. Which means that they need to work to grow their own food to put on the table.