ANSWER:
Your wife’s family has no right to influence or dictate your personal life or your child’s ability to interact with his/her grandparents.
With that being said, if your wife smothers her child or doesn’t leave the child unsupervised, this is her right as it is equally her child.
You can invite your parents over and stay with the child yourself to make sure they get quality time with him/her. Let the child grow a bit and then you can take him to spends the whole weekend with his grandparents without any interfering from her parents.