The big thing we've learned for all amusement parks - is to leave mid-day - to hang out by your pool and let everyone chill for a few hours. Then consider going back later when it cools down. Maybe one of you goes with the 7 yr old in the evening in one direction and the other does something less exhausting with the 4 yr old that includes coming back to the room earlier than the 7 yr old.
We are going again in about a month - our kids are now 14 & 17 so we can do the early mornings, afternoon siestas and return in the evenings. But - when we went years ago the kids were 6 & 9 and we could go to EITHER the early mornings OR the evenings but not both. If your kids are early risers get to the parks early, then get back to the hotel & pool for the heat of the day. Save late afternoons / early evenings for water parks, Downtown Disney, the Boardwalk, etc.
Expect a meltdown from each kid each day. If it happens you're emotionally prepared. If it doesn't happen - BONUS! Even the best of kids will get stretched emotionally. They're exhausted, excited, their feet hurt, they're hot, they're off schedule, overstimulated... So when one of them drops on a bench or the grass or the concrete and just flips out or gets the angry face / silent thing (whichever your kid is) respond by saying something like "I understand how you feel I'm really tired / hungry / hot too. Let's take a time out and figure out what to do". As parents we're trying to cram in as much as we can into the many thousands of dollars we're spending - but if we're all crabby and miserable it will not be a good vacation...and family photos will be hysterically funny - about 20 years from now.
Having the unoffical guide and following the plans is probably the best preparation you can do. We downloaded the app to our smart phone too. Good luck mama!