Let's assume he's Father of the Year. Is he really going to want to schlep a couple of kids out on tour with him? IIRC, they aren't even pre-school age. He can hire nannies and rent a house at every tour stop but it's not going to be the same as having Mom there.
I don't necessarily think he's an awful dad. I have no idea whether he is or not. But he is a very driven person and his #1 priority seems to be being the best golfer ever. Even if he was monogamous, it would be difficult for someone like that to be there for his kids when they need him. If Elin moves back to Sweden with the kids, he shouldn't have any problems flying over there to see them whenever he wants since he's a billionaire.
And it isn't just that he had an affair with the nanny either (Not saying he did but it's just an example). This was serial infidelity. The old cliche about having a girl in every town seems to apply here. It's risky health wise to do that. Just ask Magic Johnson.