I would say it can be both, it really dosen't matter, and when he gets older you can call him Mac.
Mackenzie \m(a)-cken-zie, mack(e)-nzie\ as a girl's name (also used as boy's name Mackenzie), is pronounced ma-KEN-zee. It is of Irish and Gaelic origin, and the meaning of Mackenzie is "fire-born; son of the wise ruler". The name's development was also influenced by Cainnech, meaning "good-looking". Originally a surname and male name, but actress Mackenzie Phillips has made it prominent as a masculine name for girls. See also Kenzie and Mc- names.
Aggie MacKenzie's birth name is Agnes MacKenzie.
sam- boy, mackenzie, and another girl i forgot name youngest daughter is called Claire
Mackenzie Crook's birth name is Paul Mackenzie Crook.
Mackenzie Rosman's birth name is Mackenzie Lyn Rosman.
Mackenzie Astin's birth name is Mackenzie Alexander Astin.
MacKenzie Porter's birth name is Mackenzie Lea Porter.
Mackenzie Phillips's birth name is Laura Mackenzie Phillips.
Mackenzie Mauzy's birth name is Mackenzie Grace Mauzy.
Mackenzie Gray's birth name is Alexander Mackenzie Gray.
Mackenzie Foy's birth name is Mackenzie Christine Foy.
Kelvin Mackenzie's birth name is Kelvin Calder MacKenzie.