You know... you're right. I guess I got stuck on the idea that small town Kansas 30+ years ago would not have been a place where an interracial couple or a family of color would have been able to adopt a white baby/toddler without getting serious side eye and blowback, but if they made that part of the family's struggle, and of Clark's struggle to not stand out, to fly under the radar, then I think it might actually be good story.
I don't think, however, this is a place where colorblind casting is appropriate, for those same reasons.