I don't give a shit about race so a gimmick like having super white blonde children with a black mother is not going to make me clap and jump around like a seal.
I do wonder how casting a 60 YO as a 20 something would go over though -I mean it is scoring one against ageism after all..
Ignoring the glimpses of the white women who supposed to the mother up to now:
Blonde hair is recessive.
So either she is not the bio mother or she is mixed herself, anything else gets your ass kicked on 'are you smarter than a 6th grader' for being a moron.