Edit: I just re-read your original post to see that this is a return trip for you. Some of this got a little off topic. For the mostpart, though, it's our experiences with having to alway travel in late July or Early August.
As already mentioned, the trick to the August heat is to hit the parks early in the morning, hang out at the resort in the worst of the afternoon heat, then head back for more activities in the evening. One of the advantages of going in the summer is the extended park hours. Because the parks are open so late at night, there's plenty of time to relax and nap in the middle of the day. (Believe me, it's very easy to pick out the kids (and parents) who had a nice nap from those who tried to stay in the parks from opening to closing. It may seem like you're wasting precious Disney time to do it, but the enjoyment factor for the time you are in the parks is so much higher.)
We try to make lunch our big meal of the day for most of our days. If we're going to do a sit-down restaurant, we'll plan it for lunch. The only cases where we don't do this is when the lunch and dinner menus are substantially different. For many restaurants, the only big difference between lunch and dinner is the price. And again, being in an air conditioned restaurant gives you another break from the heat.
August is prime thunderstorm weather in Florida. Plan on a thunderstorm every single afternoon -- like clockwork. The good thing is that they usually pass quickly. It will be bright sunshine, then torrential downpour and lightening for 30 minutes, then bright sunshine again. Grab a set of cheap ponchos from Wal-Mart and carry them with you in the afternoons. Many people will flee from the parks during the storms. Veterans stick it out, though, knowing how quickly it will pass. We usually pack a spare pair of socks for everyone in our day bag, because there's nothing like squishin' when you're walking around Disney after a storm. Oh, and if you thought it was hot before the storm, what until you feel it with the humidity that hits after the storm. Pfew!
Don't forget to hydrate. You won't believe how quickly the heat will take it out of you. One trick that not very many people know about is that any concession stand that has a soda fountain will give you a free cup of ice water if you ask for it. If you don't want to deal with that, carry bottles of water with you.
You'll see lots of people with battery-operated fans, spray bottles with cold water, or other contraptions to help keep them cool. We've tried them before, but to be honest, it was more a pain in the neck to carry them all around than they were helpful. If you're going to have a stroller to store stuff in, though, you might want to consider them. This is another item that is expensive at Disney, but cheap at home. Check out the summer items at Wal-Mart to find the exact same items for a fraction of the cost. Remember to bring lots of batteries for them -- another thing you wouldn't believe the price of in the Marketplace.
I'm a big guy, and the heat gets to me particularly. I've actually taken to wearing a golf towel through my belt whenever we're in the parks. It looks a little silly, but it certainly is nice to be able to wipe my brow and not be literally dripping with sweat. I bought a few of them from Disney online, so they at least have a Mickey on them. You'll also see the occasional person who has a resort hand towel with them for the same reason.
Don't even think about dressing up for the parks. Worry more about comfort than how everyone looks. You want things that breath and are loose fitting. Comfortable shoes are an absolute must.
When you're packing, keep in mind that you probably won't get away with a single outfit for each day. We practice the nap-at-noon routine just about every day. Believe me, you won't want to crawl onto the bed in the wet, yucky clothes you had on for the morning. And you certainly won't want to put them back on when you go back out. We frequently go through a third set of clothes in the evening.
If you're staying in a one-bedroom or larger, you'll have a washer and dryer in the villa. This is nice, as it allows you to keep up with all those clothes I was just talking about. Be sure to pack enough detergent and fabric softener to get you through. They'll only leave enough for one load when they clean the room. If you're in a studio, as we frequently are, we've found that the best way to do laundry is when you're enjoying the pool in the afternoon. The washers and dryers are located next to each pool. Believe me, it seems like less of a chore when you can throw a load in, then go splash around or sunbathe while it runs. One of our must-pack items in a studio is a mesh laundry bag to carry the laundry back and forth to the pool.
If you go to the pool or a water park, consider getting everyone a pair of water shoes. The concrete gets very, very hot in the direct sun. Asphalt, wooden bridges, and other places you may have to walk are downright scorching. I burned the bottoms of my feet pretty bad one year at Typhoon Lagoon, now always wear water shoes when we go. There are a few rides where you'll have to take them off, but for the mostpart you can leave them on.
Don't under estimate the amount of sunscreen you'll go through. Between the two of us, we finish off two or three bottles each trip. It's expensive at Disney, so better to stock up at your local Wal-Mart or drug store and pack it. Also think about uping the normal SPF you usually use.
For some reason, Animal Kingdom Park always seems to be the hottest to me. This is a park you always want to take advantage of morning extra magic hours. Head straight to the safari, and do it as early as possible. The animals are effected by the heat too, and will be more active in the earlier hours than they will in the heat of the day.
With small kids, even if you're not staying in the Grandstand section of SSR, you might want to consider heading over to that pool one day. There's a water play area the kids will enjoy. There's also a playground in the Paddocks section.
Also, there are daily activities that the life guards conduct each day at the main pool. These are usually games of some sort, but we've also seen DJ's and other fun activities.
Oh my gosh, this certainly turned into a book!
See you in August!
