It may well be true that Scott Walker opposes marriage equality and his wife and kids support it. But I feel like this is the next stage or perhaps the last stage of the marriage debate: GOP pols who, for whatever reason, remain adamantly opposed to equal marriage rights but who nevertheless put their families forward to say they disagree with them and are perfectly comfortable with gay people and LGBT equality.
To be clear, in this case, I'm not saying Scott Walker's wife and kids aren't telling the truth. I'm sure they are. But politically, I think the message is: 'Look, I can't be that big a hater. Even my family doesn't oppose this!' Not only does it soften the pol's image. It's an implicit signal, for those who want to receive it, that the candidate probably doesn't believe it either. He's just stuck in this position out of political necessity or inertia.