:iagree: We have dealt with this type of behavior from my in-laws. My fil has passed, but my kids have no respect or affection for my mil. It is sad, as she is their only living grandparent. Our limit is a few hours once or twice a year. Actually, at this point it has been a year since we've been there. She is not welcome to visit here. She has only been here once in the 10 years we have lived here, but she was so mean to my kids, we said never again.
You have to set boundaries, and not let them treat your kids that way. When your kids are older and see things clearly, they will appreciate you standing up for them.