Hi Alison!
If seeing as much as possible during your stay is the goal, than you certainly chose the right option!
Our family always get the Park Hopper option, primarily because we enjoy jumping from one theme park to another on any given day! But Park Hopper restricts you to Magic Kingdom, Animal Kingdom, Hollywood Studios, and Epcot. While the Water Park Option entitles you to:
•Disney's Typhoon Lagoon water park
•Disney's Blizzard Beach water park
•DisneyQuest Indoor Interactive theme park
•ESPN Wide World of Sports Complex
•Green fees for a round of golf at Disney's Oak Trail Golf Course
So in your case, you have the potential of accessing up to 9 separate places during your stay! Just have to caution that the 4 theme parks are enormous! Magic Kingdom alone generally takes our family 2 full days to get through, so even at 6 days, there will probably be a few places you may not get to on your visit. Just list your "must have's" at the top of your visit list. :-)
Hope your family catch all the sights and sounds that Disney has to offer! Have a great time!