Guess I will be the lone voice to encourage you to make the trip if you can!
We've gone several times in August. Twice in October, once in April. April was the best - temp-wise. October still insanely hot - but by then, the NY weather has changed, so there was major contrast and I felt the heat more in October than in August.
Mid-to-late August - few lines, non-crazy park crowds. Resort pools VERY crowded in the afternoons. Nice evenings. FDP may change the crowd factor...
You'll need lots of frozen water bottles, hats and sunscreen all around, and good touring plans to know where the AC is. We alternate between outdoor attractions and indoor shows and ice cream/shopping breaks in between.First time we went, I posted here and got lots of support from August WDW travellers. It is definitely do-able.
Must stay hydrated and know your family's stamina level. No commando touring in the heat. The rushing,+ heat will make everyone tired and cranky sooner.
I wouldn't pass it up if I could swing it just because it's August.

Preferable any day to overwhelming crowds, at least for me.