Hi, Amy! You are putting my math skills to work on this one! So let's assume dinner for an adult averages $30, and $10 per child age 3 and over (kids under 3 can share an adult plate for free.) We'll round that up to being about $150 per meal, and an 18% tip would be about $27. This is just an estimate. Some meals will be a bit more pricey, so budget accordingly.
Your meals at Mickey's Backyard BBQ and Cinderella's Royal Table have gratuities included in the price so you don't have to tip at those locations.
To get an idea of what the price of a meal is per person so you can get a more exact dollar amount on tipping, go to
www.allears.net and click on DINING. Restaurants with their menus and pricing are listed.
Disney makes tipping very easy. At the end of your meal, you will receive your check. Any "extras" that you ordered that are not included in your dining plan will be listed. There will also be a suggested tipping amounts. You can pay for your extras and gratuities with cash, credit, or charge to your Key to the World card. Your remaining number of dining credits will also be listed.
Hope this helps and enjoy your meals at WDW. It looks like you have some great locations planned!