There are many sites that will tell you which park/which day. Check Disney's official site and go to park hours. It should bring up a calender for a particular month, in your case chose Sept. Each day that has an EMH scheduled you can click on that and it will give you the info you need.
As far as wrist bands...yes, you will need those to ride the attractions. After 4:00 in the afternoon, they will start giving out the wristbands at certain areas in each park. You will need to show them your resort ID. Then they put the band on.
For the morning EMH you just need to show you resort ID when you enter the turnstyles in each park. At least that was my experience.