Is money earned from trading on the land of a father who neglected his children and wife forbidden (haram)? And is what they did forbidden, and what is its expiation? And are the profits from this trade forbidden, making it impermissible to perform Umrah with them?

It is not permissible to trespass on the father's land without his permission, and whatever is earned from it is unlawful (haram (definition)). The father must be informed of what happened. If he approves, there is no sin. Otherwise, it is obligatory to cease immediately. If there is a fear of informing him directly, an influential person with him can mediate. What was mentioned about his negligence in providing sustenance and other matters should be referred to the judiciary.