We are in a very similar situation. (Ex)H and I are both teachers, so we always went during the summers (Aug) as the kids were growing up.
Now DD21 is also a teacher, so DS23, DD21, and I will be trying the Wed-Sun after Easter this year to avoid the humidity of August.
DD21 just went with her father from Dec 26-Jan1 and said crowds were only terrible Dec 30 and 31, but she loved the weather.
We are of the mindset that we are fortunate enough to have been many times before and will have many more trips in the future, so we don't need to see and do everything. I expect to be hot, but it has to be better than the oppressive heat and humidity, that doesn't even go away at night. At the very least, I expect pleasant mornings and evenings.