Hi.
My parents split when I was 5 and from what I remember I handled it quite well.
they took turns with christmass and other holidays and sumtimes shared the days, ie one morning one arvo.
The main thing is that your both there for him. I think the reason it never affected me much was because dad was always around and he didn't move out of town till I was in my teens and then he would come down to pick us up on the week end.
As for partners, my father always introduced them as good friend and wasn't till I was older that I realised they were girl friends, only knew my step mum was cuz they got real serious.
Hope that helps from the kids point of view.