I know you are playing it by ear, but I highly suggest you pick up The Unofficial Guidebook to Disney. It is huge and intimidating, BUT you can easily use it. Promise! You can get it at the library. last year's will work. There are sections for each park. Focus on that. You won't need to look at the other stuff. Again, don't let the size intimidate.
For each park they call them "headliners." Those are the ones, such as "Soarin'" at Epcot (the front) that many people love. I can't emphasize enough that just a little pre-trip planning will really make your trip special.
Nope you don't have to over plan every single minute, but my best friend and her family went, without any planning. They missed so many headliners that they would have loved. YES they still had a blast, but I think it should be a choice to skip attractions, versus you never "ran into it," so didn't know about it.
You can also easily survive eating from all the counter service, but I would go to the Disney web site, and see if you can get one or two sit down meal reservations. It is so nice to sit in air conditioning and take a break for your feet.
Be sure you understand how Fast Pass works and use it.