It pays to research your options. Usually with a WDW ticket, the more days you stay, the cost per day goes down. So it probably makes sense to add your arrival and departure days to your ticket! You definitely have time to spend lots of times at the parks based on the hours you gave us.
I myself always get the "hopper" feature on my park pass, but some people never use it at all. It's nice to have, especially when you go during crowded times of the year, like August. You can hop from park to park as needed. (But, if you decide not to add the hopper feature up front, you always have the option of adding it after you get there if you decide to hop!!)
It probably doesn't make sense to add the "waterparks and more" option to your base ticket, since you will only be going to a water park one day. You can usually purchase a one-day water park ticket for less than the cost of adding the "water parks and more" option to your ticket. (Plus, if you add the "water parks and more" option to your ticket and don't end up using it, you're out about $50! That happened to me on my last trip - frustrating!)
Keep reading these boards for more tips about planning your trip - the DIS is a wealth of information!