exerda

There is no need or requirement to tip more at the holidays. It's up to you.

On the second question, it's becoming more common for restaurants to have no-tip policies (and thus tip-inclusive prices). I've dined at several in the past year. Most didn't even offer a tip line on the credit card slip. But they also will almost certainly tell you: "The tip is included in the price," and they are almost entirely rather high-end, high-priced places to begin with.