I disagree with the statement…………….
A father in Law should keep his mouth shut and wallet open.
A good father in law keeps his ears open and only opens his mouth to give advice when asked or if he sees a truly dangerous situation.
If your child is now old enough to get married, your child is old enough to make decisions and mistakes along with his/her spouse.
BTW> my mother Z”L always said a good MIL keeps her mouth shut and her refrigerator open.