We probably wouldn't do a water park as a break. That's JUST MY OPINION THOUGH!! The water parks tend to get busier during the afternoon. Will you be hauling your swim gear with you to the parks? If not you'll lose time transporting to resort. Water parks are also tiring, though you might not think so.
As for AK, if you're trying to sit for a period of time, I would suggest finding a table at Restaurantosaurus. It offers quick dining for lunch and dinner. I think it opens around 11:00. It is a big place and if you time it right you could find a table off in the corner, or even a table outside underneath some shade.
Have a great time. September will be a good time to visit.