I haven't taken the time to read the previous posts....I'm sure you got good advice, including, 'don't go during the summer'!!!
I've been several times...and yes, it's hot. Surface of the sun hot!!! And the humidity is not to be believed. I went once during a hurricane...Charley. Interesting experience.
Then, our last trip, back in '10, we were there just about a week earlier than your time frame. And of course, Orlando was having record breaking heat. And the following Dec?? Record breaking cold...I just couldn't catch a break that year. And when Orlando is having record breaking heat? In August??? There are no words.
So, with this in mind...this is what we do...
1. hit the parks early, every single day. If the parks open at 7am..be there, early. You need to be there as soon as they open.
2. Leave the parks by noontime. Go back to your resort and relax. Swim (although the pool will be tepid), shower, and cool off. Get your feet up for a bit. Yep, watch some tv...whatever.
3. Return to the parks late afternoon/early evening. This is when we normally eat our dinner. We book a dinner ADR for table service. Your body needs fuel...even if it's 108 gazillion degrees!!! So, sit, cool off, and eat....slowly.
4. Drink more water than you think you could possibly need. Then? Drink some more. I like to try for a bottle of water every 90 mins or so if it's really humid. And be sure to make potty stops every 60-90 mins. You will need to potty more often, obviously. But you can also rinse off with some coolish water...that really makes you feel better.
5. Wear a wide brimmed hat...with a strap so you don't need to worry about losing it.
6. Wear short sleeved shirts. I know it sounds hotter than tank tops, but keeping that sun off your back and shoulders is a huge plus!!!!
7. Sunglasses...your eyes get really tired in that light for that many hours on end.
8. Drink some more water.
9.Stay in the parks as long as you want once the sun goes down.
But remember...your body is working overtime to stay cool. Don't push it too far or too fast. Take your time. Stop and relax in the parks. Find a park bench and plop yourselves down and people watch for a bit.
The summer time in WDW is not a time for commando style touring!!! Especially with a little one.
I know that when we were there in August '10, my dh left and went home on day 7..he had to go back to work. But my dd and I moved from BWV over to VWL for the next 4 nights. It was so hot for the first two days that we would go out and get breakfast at Roaring Forks, and go back to the villa and stay there all day, to stay cool. We went out again at about 5:30 for dinner ADRs. Now, I don't advise that to everyone. We have been to WDW more times than I can remember, so staying our rooms for those hours on end wasn't a loss to us. And we had some great bonding and discussions. Not often I get my teenaged dd (then 16) to myself when she can't really get away!!!