If the park is opening at 8 for EMH, you should be fine. Arrive no later than 7 at the tapstiles, not just going through security.
They will let you in earlier than 8 and hold you at the entrance to Pandora. Walk quickly as the line does build very quickly.
If you near the front fo the line, you should done by 8:15, assuming you got in early.
Navi should be walk on.
Depending, many times Safari is not open for EMH, so check that to be sure. You may have time for Dinosaur and Everest instead. Safari should be open around official park opening time.