I'm not a late person but I watched an episode of Dr Phil once where he said that there is only one reason for lateness and that reason is arrogance. Arrogance that the 'late' person thinks they can get somewhere in 20mins, when it actually takes half an hour. The arrogance also shows itself in that the late person thinks that their time is more important than anyone else's.
I have never considered having 2 children an excuse for being late either. When they were young and in nappies etc, I just used to leave earlier and predict what child related scenarios could make me late and adjust accordingly.