I was thinking more about the assumed background for characters in Slithdale Hollow. All the children are part of the same family, which in turn seems to imply that all the characters are of the same race or ethnicity--and that kinda bummed me out because I'm just not into locking players into a narrow conception of who they can play.
But then, the more I thought about it, there's no reason why the Wycherly children have to all have the same skin color. Their parents already have an utterly impossible numbers of kids, so it doesn't really stretch things to also note that their children represent all colors. Think a really dreary United Colors of Benetton and you've got the right idea.
In fact, I think this makes the uncanny "something is strange here" nature of the family even more interesting. Clearly, all of these children cannot be born of the two people they call Mother and Father--even though everyone in Slithdale Hollow acts as though they are. The children's origins are just another mystery to be explored by the characters in play.