It honestly just depends on the time of year.
Right now, at IOA, the only thing that seems to be opening later than everything else is the Jurassic Park Discovery Center (10am). At USF, Disaster begins running at 10am. Fievel's Waterslide opens at 11am. Woody Woodpecker's Nuthouse Coaster is opening at 10am.
Of course, all the shows usually begin late morning.
I know at slower times in the year, JAWS opens around 10am.