Non Disney resort guests are not asked to leave the evening EMH park. Only guests with wristbands are allowed on the rides and attractions. The Cast Members are very dilligent in checking for the wristbands. So you can stay in the park to shop, eat, and look around if you are not a Disney resort guest. But you cannot do any of the rides or attractions once the evening EMH begins.
For the morning EMH you must have a Disney resort ID to enter the park. For the evening EMH wristbands are distrbuted after your resort ID is scanned.....and this is done for everyone in your group.