I have a private tour guide/ van driver for a 6 day 5
person trip. They will be with us continually. How to calculate tip? Percentage of tour guides salary? Percentage total cost which is 6747 Euro? If the latter, that'd be 675 or about 23 Euro per person per day at the high end of 10 percent.
First I would make it depending on how much you were happy with the perceived value. In this price class for the service a tip is no automatism. I recommend to communicate early with what you are happy or not with a concrete wish how to change it.
Just stomach feeling: 50 EUR per day is fair when you are happy. Feel free to increase when you are very satisfied.