You are in a very precarious situation.  If ther eis a court order in effect that states what the visitation is supposed to be then you can not violate the order.  And you need to explain to your step son that if he puts you in the position of violating the order you could be sent to jail.  Now, what you need to do is to attempt to modify the order but really you wish to terminate the visits and it is unlikely that the court will let that happen.  Courts view the matters in the best interest of the child.  Good luck.