Stay offsite. I know that renting DVC points saves money, but it saves on the cost of a DELUXE resort. We rented a studio at Boardwalk Villas over Columbus Day weekend and it cost me $209 a night. YES, it saved me over $200 a night if I'd gone rack rate with Disney, but it was still $209 for a studio villa that sleeps 4. To us, that's a splurge, not a way to make the trip more affordable.
If you want to do a character meal, do breakfast. While character meals seem to be quite the splurge, they will save you TIME, and at Disney, time equals money (because you've seen the price of park tickets!). At Crystal Palace, you will meet Pooh, Tigger, Piglet, and Eeyore. It can easily take 2 hours of waiting in line in the parks to meet all 4 characters, if not longer, so this is something to consider when planning your trip. Breakfast is cheaper than lunch, lunch is cheaper than dinner. However, if you book an ADR for the latest breakfast seating and are still there when they set out the lunch buffet, you can continue eating lunch foods for the breakfast price; you just have to be seated during breakfast. This is a cheaper way to get your kids filled up mid-day, and you could do something light/simple at the condo for dinner. Same deal at lunch-our ADR was for 3:30, which was still lunch time, so lunch prices. However, by the time we could be seated, order beverages, and watch a tad of the parade passing by outside, they'd set out the dinner buffet. We ate and only paid for the lunch price. I am not advocating character meals as cheap, but if you have kids who HAVE to meet a special character, sometime this is easier than waiting in long meet-n-greet lines (especially in August!).
I am not saying this is a way to fund your vacation, but sometimes DVC offers gift cards for doing the time-share tour of their properties. DD and I did this and it was easy-peasy. It took us about 2 hours from pick up to drop off, and we got a $150 gift card for doing the tour. Your oldest kids could take the youngers to the park while you and DH do the tour, and DVC will drop you off at the park of your choice after the tour! This can be iffy, as DVC offers a variety of incentives that sometimes aren't as lucrative, or you might not want to spend your time this way or know where to find a DVC kiosk, but if it's offered to you, it could be worth it.
IF you are eating in the parks, share meals, especially at lunch time. Peruse the menus available online before going and eat at places that offer good deals. For example, DD and I always share the BBQ chicken at Flame Tree BBQ in AK. It's a full half-chicken with cole slaw and beans. I eat the dark quarter, she takes the breast; it's as much chicken as either of us would eat for supper at home, and we share the beans and cole slaw. I think it costs about $10. COuld you bring PB&J for cheaper? Sure
but this makes everyone feel like they "ate out" and I'm not sure where else you can do take out for $5 per person and get a full meal. You can also find deals like this at Cosmic Rays, or share platters at any of the Epcot counter service locations, and don't forget to consider splitting double burger meals, or ordering off the kids menus at lunch time. Especially if it's hot outside (you did say July/august, right?), many folks don't like to eat a big meal.
IF you aren't eating in the parks but don't want to do a whole lot of cooking, Olive Garden take-out can be a good deal. We have discovered that OG provides huge salads with their take out meals. We order half of the meals with salad (or fewer than half) and the rest with soup. We share the salads at dinner, and save the soup for another lunch or dinner. I know, OG isn't necessarily cheap, but if you are sharing meals or ordering kids meals, being able to stretch the salad and soup to be part of another meal helps with costs.
If you are cooking in your condo, bring spices from home. You can really jazz up a cheap meal if you have some garlic powder, chili powder, basil, oregano, and cumin with you. Just pour from your home stock into little baggies. My aunt has been known to bring big containers of frozen meat (spaghetti) sauce with her. They'll have it on pasta one night, and then she throws in chili powder, more garlic, and cumin to turn it info chili w/rice for the second night
leftovers are put on tortilla chips with cheese, lettuce, tomato, etc., and becomes nachos for the third night. Italian goes tex-mex just by adding the right spices!
No souvenirs. The trip is the souvenir. If you MUST buy everyone something, go to the Disney outlet and buy things cheaply. We have scored tee shirts and towels for less than $10 each. One year we got sterling silver charms for $5 each- and characters that I couldn't get in the
Disney Store at home.
Definitely look into the cost of 4 day park tickets with waterparks and more. I don't know if they are cheaper or not
but definitely worth looking into. Touring the theme parks in the summer is brutally hot entertainment; it might be nice to intersperce park days with water park days! I wouldn't pay for park hopping, though. Is it nice to change parks? Sometimes, especially if you want to have dinner ADRs in Epcot/World Showcase most evenings, but it's totally not necessary to park hop to have a wonderful time at Disney!