The southern kids go back to school in mid-August. If your visit is before school is back in session, it will still be very busy at SW. If your visit falls after the Florida kids have gone back to class, it should be somewhat more manageable (especially on weekdays). I'm not certain what date the local counties kick off the school year in the Orlando area.
You will get quite a few northern visitors at that time of year, as most students up here don't go back to school until after Labor Day.
If the new Infinity Falls is open by the time you visit, I'd definitely plan to go there early in the day before the crowds swell. Manta, Mako, Kraken and Antarctica: Empire of the Penguin also tend to get lengthier lines as the day goes on so should be done at park opening or shortly after to minimize wait times.
Definitely try to see Dolphin Days, One Ocean, and the Clyde & Seamore show....they are all awesome.
Plan to spend $10 on animal food: it will be money well spent. Trays of fish are $5 each or 3 for $10, so that $10 purchase will allow you to feed the sea lions and seals, the sharks, and the sting rays. Super fun.
If you're going to be there all day long, consider purchasing the dining plan. One restaurant serves a continental breakfast (cereal, muffins, croissants, danishes, and fresh fruit) and then you can dine once per hour (one entree, one side or dessert) for the balance of the day. Lots of different choices: barbecue platters, fajitas, Asian dishes, pasta, fried chicken, burgers, wraps, subs, pizza, and even fresh pretzels. Sides range from fruit to cake to massive pickles to fresh salads. Beverages are unlimited and in the heat of August, you could easily drink your plan value in bottled water over the course of a full park day.
If you wanted to add an affordable extra to your day, consider the Dolphin Encounter. It is $15 a person but you get to touch and interact with a dolphin.....and park photographers capture some great photos if you want to purchase one.
