This happened to us all the time. Finally, with the last card and check, we just told them, "Unless we hear from you, we will know that you do not need this gift so they will stop. It doesn't take long to say thank you". These were 15 and 16 year olds. We have 18 grandchildren and now great grand children. It is difficult to be able to afford to keep sending the money. We told them that the only notification was when the bank let us know the check had cleared. And, it isn't always the parents fault.