For character meals, book the last seating possible when making ADRs, that way you can spend more time w/ the characters.
For counter service meals, I usually order a kids meal. It's way cheaper and always plenty of food.
I also completely agree w/ Thumper's Tara, get there at park opening! We like to do this, then go back and nap at the hotel or pool in the afternoon and head to a different park at night.
Make sure your guests know about Fastpass. We always grab a FP for our favorite/ most popular ride as soon as we get into the park.
I do not know if I should post this or not... but I'm going to anyway

We like having a big breakfast and often do buffets. We always take an apple, banana, or orange with us from the buffet for a snack for later. That way we don't have to spend $ later.
Good luck

I am sure so many others have great tips!