Yes, August is busy. So are the other 11 months! Plan on crowds, lines and heat/humidity.
I agree that food is expensive and you should take your own as much as possible. Take stainless steel water bottles - DO NOT use plastic water bottles especially the suggestion that you freeze them and use them as ice packs! Freezing plastic is not safe because the bottles are made with petroleum products!
Some people like those personal fans and mister bottles. Fine if you want to.
Take an insulated backpack or a couple of them so you can split up the load. Take high energy snacks like nuts and trail mix, string cheese, fruit slices, and so on - the kids can snack while waiting on line. Take sandwiches if you have a way to make them - you are allowed to take your own food and eat pretty much anywhere. If you have a small fridge in your hotel room, you can keep some things in there, and of course peanut butter can sit out all week. I always pick up a small bottle of dish detergent so I can rinse containers and utensils and just drain/dry them on an extra hand towel.
Some people take small electronics to play with in line, but you have to be sure your kids will put them away and not want to use them while walking along! They really need to experience everything they are seeing: the engineering feats and special effects, the diverse crowd, the chance to chat with people in line and find out where they are from, the characters roaming the grounds, the topiary, all the decor, and so on.
Go early in the day, and go to the back of the park. The kids will want to stop at the first rides/attractions they see, and so will everyone else. One of the "unofficial" guide books gave us this tip and it worked great - go to the back, where there are fewer crowds, then work your way back toward the entrance. When you're wiped out, you're ready to exit directly to the monorail or buses, whatever transportation you are using. Head back to your hotel or condo, and plan on naps or quiet time or sitting in the pool. They will be wiped out, and so will you.
Wear good sneakers - no sandals or flip flops. There's a whole lot of walking and standing! Sunscreen, hats/visors, the usual protection. We go to the dollar store and get a couple of those cheap rain ponchos - there's often a sudden shower in Florida, which can cool things off, and the ponchos let you keep on going! Disney sells them for a small fortune but go for the cheap ones from home that fold up into a tiny packet!
My neighbors took advantage of some new express passes. There's a cost involved, but they let you go to a ride, check in, and then you are given a time to report back. Sort of like making a restaurant reservation and getting one of those vibrating sensors, you know? But you have to get back to the ride within a tight window of the reserved time, so it's not a good time for going to another ride, although you can go sit and eat something, use the bathrooms, or browse in a shop if there's one nearby.
Have a plan for meeting up if someone gets separated. Disney employees are awesome at assisting and dealing with emergencies.
Prep the kids up front for a budget - they will want to stop at every ice cream and lemonade stand, buy every souvenir, and so on. Aside from the expense, you'll be carrying souvenirs all day. Figure out a way to buy them on the way out or on the last day - let them look for a few days to decide what they really want and what's within budget. I think it's okay to say that you can buy everything on line, or "we're not buying anything on the first day, period."
Have fun!