That week is very busy with people. Best to start in the Studios and get there before they open. Then since you have park to park tickets, when you are done in the Studios, take the train over to Islands. But do not take the train any later than around 3:30 pm, because the line just gets longer and much longer as the park nears its 5 pm close. And from experience, even with express, was a long wait when I decided to ride it around 4 pm. If you are closer to that closing time, it’s faster just to walk over to Islands. Not as many enter the front of Islands later in the day.
Know many stay in the Studios to be held in the park fenced off areas, after close, to wait for HHN to start. You will see crowds increasingly coming from City Walk pouring into the Studios by mid afternoon.
Islands gets a little busier when the Studios close, but can be manageable.
I used to go the first two weeks of October. Began to be too busy and more expensive, so now I go near the end of September, when crowds are not as many, except on the weekends.
Anyway, my two cents, and hope you have a fabulous time the day you go.