our grandson and his wife have invited us to a show and dinner that includes his wife, her parents, his parents and ourselves. it is her parents wedding anniversary as well as our grandson and his wifes'. the question is...are we responsible for the parents dinner? since it is also our grandson's anniversary i feel it is right to pick up the tab for their meal. but as his wife's parents are also celebrating should the kids pay for them while we pay for the kids?