Ann Dunham has motive to have Barack Jr. born in Mombasa.
She thought Barack Sr. was a heir to royalty and having Jr. born the Africa would solidify his future as a leader in an emerging nation.
Last time I checked, Africa did not have a 14th amendment. Thus, dropping Bambi in Mombasa would not have added anything significant to his prospects of becoming a leader in that continent. Whereas, dropping him in Honolulu was necessary to his future becoming Leader of the Free World. Not that any of this was occupying Stanley Ann's befuddled eighteen-year-old mind.