How can parents protect their children from unfit grandparents?

In general, grandparents have no rights when it comes to time-sharing for minor children. Those rights are reserved to the parents. If grandparents are going to spend time with the minor children, they will need to piggyback those rights with the rights awarded to their children. However, sometimes you have a situation where a parent, in this case we’ll just call it a father, is provided time with the children. He then lets the children spend most of that time, or a lot of that time, with his parents who you feel are unfit. That’s a little bit more difficult to deal with. However, there are concepts such as a right of first refusal which can be drawn into marital settlement agreements or can be awarded by courts through contested litigation wherein if a parent can’t take care of a child during their time with the child, that the child shall be returned to the other parent as opposed to spending time in daycare or with a grandparent or some other third party.