Birthday dinner...or not

My son was supposed to go to dinner with me and my girlfriend until I told him it was Saturday, which is the day we always do things.
"Can't you change it?" was his reply. He told me his Mother told me he had to go to his Grandparents for his cousin's birthday party. (A 5 year old girl)

I told him that was the day we were going out and he knew it, and why should I always have to change my plans for somebody else.
He told me he would tell his Mother he was going with us.

I insisted that he do that right away since it was not fair to her to tell her at the last minute.

The day of the dinner I asked him if he had talked to her and he said yes. I asked if she was OK with it and he said, "I'm going with her, she told everyone I would be there."

The "guilt trip." I thought by now she would have suffered enough guilt of her own to be dumping it on someone else.
But, she always surprises me.

I went to dinner with my girlfriend and had a nice dinner. I asked a friend for a recommendation and it was quiet and relaxing.