Hi Angela,
I'm so glad you have stopped by the Disney Parks Moms Panel with your planning question. I am sure you are getting really excited about your upcoming trip.
Your current plan for days at each theme park sounds very similar to how I would distribute my time. Deciding upon whether or not to go to one of the
water parks would depend on the time of year, in my opinion. If you will be traveling during the late spring to early fall, I would recommend possibly swapping out one of your Magic Kingdom days for
Typhoon Lagoon. Epcot, in my experience, is large enough to go for two full days. But, that is simply my feeling.
Another thing to consider is the ages of those traveling with you. I still have small children and I prefer to spend some time at the resort pool rather than an entire day at the water park. My little one wouldn't have been able to last all day. However, as they get older and can do more of the water slides based on their height, I'm sure that the water park would be a huge hit.
I hope this helps you in your itinerary plan. Have a magical visit.
~Allison L