Is it permissible to take one child's toy to quiet another child, and is this considered an infringement on another's property?

It is not permissible to take a child's toy, which he owns, to give it to another child, because that would be donating his property. It is not permissible for the guardian to dispose of the ward's property except in a way that benefits him. A gift without compensation brings no benefit to the ward and is considered pure harm.