First I would make a general plan. If you're going this July, I would do that right now. This will give you a beginning plan and you'll know where you'll be if you want to plan any PS's for meals. Check out
www.wdwinfo.com as suggested and if you want buy the passporter or birnbaum's just for the basic info. They are all loaded with suggestions.
Are you going to use EMH or not.
If using EMH---you'll know what day you're going to be at what park. Most people using EMH take advantage of EMH, then either take a break and hit another less crowded park for the rest of the day.
If not using EMH, you can get a list of the "least crowded" days for each park either on the website or in a book.
For either one, get their about 1/2 to 45 minutes before park opening, do the headliners first thing. If you get them done in the first hour or two, your day all of a sudden (HOPEFULLY), takes a "reverse warp". You're ahead of the crowd and can do the less crowded rides leisurely, take time to smell the roses, a break, or use FP to hit the other headliners.
Once I knew where I'd be when, I would quickly choose restaurants and make my PS's. I would do that right now too, especially for July. You can always cancel.
Everyone has their favorites. Here's ours---Le Cellier, Artist Point, Chef Mickey. Ones we think are nice--- "The Plaza Restaurant" and Sci Fi. ESPN club if your 10 y/o is a boy. We've tried allot, but have allot more to try, these are ones I consider very recommendable.
I agree with overplanning too, just a general plan, some ressies, and general park/ride knowledge will help you save some time though.
Simply, have a "general" plan of where/when.
Check out the restaurants you'd like to go to and make your PS's.
Be aware of the headliner rides that would waste precious time in line. Either do them first thing upon park opening, or use FP, just so you know which ones you're going to have to plan for. Again, only to avoid hours in line.
Make sure you plan in what you'd REALLY like to do and plan that in to for sure do. You cannot even begin to get EVERYTHING in.
Things I wouldn't miss~~~
All the night time shows
For all girls-maybe a "sleep in" day, with a really nice relaxing breakfast, and maybe shopping around Downtown Disney, a manicure/pedicure, would be fun too, even for the 10 y/o. If your 10 y/o is is a boy, he might enjoy Shark Reef at Typhoon Lagoon and the wave pool or Disney Quest.