Hello, Warren!
Your first trip to Walt Disney World! How exciting!
We use this exact same type of ticket when we take our high school senior class trip to WDW; it's a great way to explore the parks. If you take a look at the explanation of how
Magic Your Way Tickets work, you'll see that a four day Park Hopper Option entitles you to four days at the four major parks (Magic Kingdom, Epcot, Disney's Hollywood Studios and Animal Kingdom.) You have also entitled yourself to four days of visits to both of the two water parks, Disney's Blizzard Beach and Disney's Typhoon Lagoon. All of these visits are valid for 14 days from the day of your first use, and you may upgrade them, in person, "if entitlements remain within 14 days of first use."
Just one note: according to Frequently Asked Questions, located on that same site, "visiting multiple venues in the same day will use one Water Park Fun & More entitlement for each venue visited. For example, if you visit Disney's Typhoon Lagoon Water Park in the morning and DisneyQuest Indoor Interactive Theme Park in the evening, you will use 2 visits from your Magic Your Way Ticket." This is because the Park Hopper Option applies to the four main theme parks only. The others use one ticket each, even if two are visited on the same day.
I hope that this helps to clarify things! Please send more questions as you think of them! I'd love to help you plan this first fantastic trip!