I just bought a goose as a pet to accompany my children, and I don't know how to keep it.

Goose can eat grass, leaves and so on. You can search related matters online.

But I don't think geese are suitable for pets, especially indoors with children. There is no way to train geese to go to the toilet. Because birds do not have the ability to temporarily store excreta in their bodies, in order to reduce their weight as much as possible to adapt to flying life, excreta will be excreted as soon as it is produced. Because of this, geese will excrete everywhere, making your home very dirty. Moreover, geese are fierce and can strangle people with their mouths, which is especially dangerous to strangers and children. This is why "there are few geese as pets".