We did Blizzard Beach on the MK Saturday and the crowds were not bad. All in all, throughout the entire week, the crowds were moderate at the parks. We did Universal, IOA, and WDW for two weeks and the crowds were manageable.
I felt the heat was pretty miserable this trip. Bring lots of water and squeeze breezes and get into the air conditioning when you can during this time. I come from a dry climate, so the heat and humidity were difficult for me. My DD suffered from some heat exhausation one day at Universal. She got to the point of getting sick to her stomach that evening. Popsicles and gatorade did the trick to bring her back to normal, but we got quite worried for a bit. Don't over do it and you should be fine.