Hi, Beverly!
Welcome to the Disney Parks Moms Panel! I love the "Plus Pass" option, so I am happy to help you sort out exactly what you need for three full days of magical fun at Walt Disney World Resort®.
To enjoy two days at the theme parks and one day at a Disney Water Park, you will need to purchase a
Two-Day Park Hopper Plus Pass. With this pass, you will have two days worth of visits to the theme parks, with the ability to park hop to all four - so even though you're planning an Epcot day and an Animal Kingdom day, you can visit them all. In addition, you'll get one water park day (the "Plus" part), this visit does not need to be on a day that you visit a theme park - in fact, you have 14 days from the day you first use your ticket to use up all your visits, giving you the option of spreading them out even more! The most magical part of it all, it's only $15 to upgrade to the Park Hopper Plus Pass. That's a great deal!
I hope this is helpful, Beverly! Please do not hesitate to let me know if you have any additional questions. Now that you know what pass you need, I'd love to help you continue planning.
Faith