Am i a Mc or Maclennan

Hello there new to all this forum stuff.Due to get married next year and just trying to clarify if im a Mclennanor Maclennan.Family rumour has it that a mistake was made somewhere back on perhaps my great grandfathers birth cert resulting in family thereafer becoming Mc instead of Mac.Myself and all my family o fathers side are Mc (on birth cert) though they all spell it Mac.Just want to get it right for my good wife to be.
My grandfather is Kenneth Maclennan from the isle of Barra (Scotland) and i believe is father was Murdoch possibbly from North Uist.Can anyone shed any light, i would be grateful thanks.