Upon their arrival in Hawaii, Amelia Earhart and Paul Mantz went to the Waikiki beach house of two of his friends, Chris and Nona Holmes, who had arranged a party for them. This is when we believe the photograph you have was taken. The woman second from left (wearing leis) is likely Terry Minor, Paul Mantz's fiancée. The man and woman beside Earhart are most likely Chris and Nona Holmes. Howard Hughes is not in the photograph.
If you wish to learn more about Amelia Earhart's life, and her time in Hawaii specifically, you can read about it in the book Amelia Earhart: A Biography by Doris L. Rich. I have enclosed a photocopy of the book's title information and the page relevant to your photograph. I am also enclosing the copy of the photograph you sent to us.
I hope you will find this information helpful. Thank you for your interest in the National Air and Space Museum.
Regarding the DC-3: I would like to know what the appendage is on the right side of the fuselage in front of the intake and behind the copilot side window? This is very clear in the photo of the aircraft hanging from the ceiling of the museum. I believe that the air intake is for the cabin ventilation and thought the airfoil looking like thing may be a form of vortex generator. I have asked fellow pilots and all though we have flown in a "3" no one knew what it was or its purpose.
Your conjecture is basically correct. The airfoil shape is there to smooth the flow into the air intake immediately aft of it. Our Aero Curator indicates that this was found only on the "original" Wright-engine powered DC-3s, and is not on the Pratt-powered DC-3As/C-47s. Apparently, others have previously asked about this device. The NASM DC-3 is a Wright powered aircraft built in 1936.
I'm old enough to have flown in DC-3's still regional in airline service in the early 1960s, and I never realized that the earlier models had differences in addition to the Wright powerplants. Thank you for giving me the opportunity to add another tidbit to my store of aeronautical trivia. We hope to be of further service in future inquiries.