Hi Kelly and welcome to the Disney Parks Moms Panel.
First of all, congratulations on securing a FREE Dining promotion - this is a fantastic way to save money when visiting the Walt Disney World Resort.
As you quite rightly say, gratuities are not included with the
Disney Dining Plan except at Dinner Shows, Private In-Room Dining and Cinderella’s Royal Table.
An automatic 18% gratuity charge will be added to your bill for parties of 6 or more.
The 18% gratuity is calculated on what the cost of each Table-Service meal would be if you were paying out of pocket and the best way to get an idea of what this cost is likely to be, is to take a look at the menus section of the unofficial website www.Allears.net.
From here, you can select which Entree, Dessert and Non-Alcoholic Beverage or Full Buffet / Family-Style Meal you would be likely to choose for Lunch/Dinner at various Table-Service dining locations and based on this cost, calculate what the 18% gratuity charge would be likely to be.
Wishing you a magical trip filled with memories which will last a lifetime!
Emma