This is just an interesting observation more than anything else. It's a done deal and I think it was handled properly, but I just have to wonder to the chowhounds what some people (servers) are thinking.
We have a brunch buffet that we enjoy frequently at a nice, higher-end hotel in the near-by city. Today, to say "thank you", we brought friends that had done us a good turn. We were a party of 6, total, including our 10 yo kiddo. Truly, this is a wonderful buffet in a lovely atmosphere and we've never been disappointed. Today was no different. Excellent food!
Later this afternoon, dh, kiddo and I were taking a brisk walk and dh told me about the bill paying transaction. They have a children's price for the buffet, which was not reflected on the bill. He must have done it very discreetly, as I didn't notice, but dh mentioned to the server that one of the charges should have been for a child. He said that she seemed a little put off, but took the bill back. When it returned, it was calculated properly, but now with an added 18% gratuity. (FTR - the restaurant has an automatic gratuity for parties of 8 or more.)
So... dh didn't leave more tip. He was peeved, and I don't blame him. We're good tippers. Service was fine (not exceptional... but it was a buffet!) and we would have left a much bigger tip. As it was, I think her actions were inappropriate because it was not restaurant policy, and in the end was to her own detriment. I was happy that dh handled the whole thing without anyone else at the table realizing what was going on! I think he did the right thing. I don't know what else he (we) could have done.