I've never been to WDW in August, so I can't comment directly on that. But from what I understand, HOT and CROWDED are good descriptions. There are ways of dealing with those issues.
Go early!
I would want to be at the MK as soon as you can get in. You'll only be able to get as far as the hub, but you'll beat a lot of the crowd to the rest of the park!
(Past experience: we did this and went straight to the Winnie-the-Pooh ride. As a result, we got to ride the ride with Eeyore which was a big hit with the young and young-at-heart in our group.)
Fastpass, fastpass, fastpass!
Use it often and use it wisely. I would expect long lines in August so Fastpass can save you time. If there are a few attractions you want to see in an area (say, Space Mountain and Buzz Lightyear in Tomorrowland), get a Fastpass for one and get in the standby line for the other. Just watch your Fastpass return window times.
(Past experience: While the rest of us waited at Pooh, my wife got Fastpasses for everyone for Space Mountain. Due to short lines, we were able to do several Fantasyland attractions and then used our Fastpasses to walk right on, past a very long line, to Space Mountain. We were also able to get our next Fastpass for Buzz BEFORE we used our Space Mountain Fastpasses. We frequently sent someone ahead to collect the next Fastpasses whenever possible.)
Baby swap!
I don't know if this applies in your case, but if one or more of the kids sits out with a parent, use the baby swap. The cast members at each attraction can explain what you need to do. In essence, everybody else rides and then when they come out, the people sitting out (and sometimes others) can get right on the next car/boat/train/etc.
(Past experience: We had two kids under three so that left them out of the roller coasters and other big rides. We had two people sit out with them and we usually got two or more babyswap passes each time. That meant that anywhere from two to six people got to ride or ride again right away! My nieces hit everything twice this way. You get at least as many passes as those who sit out, but sometimes we almost got everyone else back on the ride.)
Don't criss-cross!
Try to hit everything in each land of the MK together. Nothing will waste more time and energy than running from one end of the park to the other. Of course, your specific situation may require it on occassion. So map out your "must-sees" and group them together by location.
(Past experience: We just do this every time we go.)
Take that break!
By mid- to late-morning, it will get crowded and hot. Take this opportunity to leave the MK (don't forget that re-entry handstamp!) and ride the monorail to one of the resorts for lunch. That way, you get a break (the resorts are very quiet mid-day) and you get to ride the monorail too! The relative serenity of a quiet lunch break will save your sanity and recharge your batteries for the rest of the day. Eat at an atypical lunch time (before 11:30 or after 1) for shorter lunch lines.
(Past experience: Our personal favorite is the Kona Cafe at the Polynesian. The resort is very quiet and peaceful and the food at the Kona Cafe is great. When you get to the monorail station, don't forget to ask if you can ride up front with the conductor. It can't always happen, but sometimes you get lucky.)
Parades: see them or skip them!
If you want to watch the parade(s), you'll have to stake out a good spot early. If you don't mind missing the parade, it's a good time to hit the rides because so many people are waiting for the parade, the lines are usually shorter.
(Past experience: We're not big on parades, but the last time we were there, we could have had a great spot for the nighttime parade near the Splash Mountain/Big Thunder Mountain bridge in Frontierland. I'm sure other people have other suggestions.)
Stay late!
It will be cooler and the crowds should be more manageable. You can ride the rides all the way up until closing time and you usually have at least 30 minutes to get out of the gates. Don't worry, the cast members won't let you stay inside, but they won't rush you out either.
(Past experience: We watched the fireworks from the town square on Main Street and then just sat and watched the mobs crush out of the gates. It was very peaceful and fun to not be in that mob. We sat until the big crush was over and we still weren't the last ones out. Plus, you can hit the Main Street stores at your leisure without the mob.)
Thanks for listening and hanging in there this long. Sorry for the length of the post.
If I can clarify anything or answer any questions, let me know.
Have fun!
