Being Natasha's and Yelena's child is anatomically not possible(you know what happens in the Red Room right?). I think I would be Wanda's child, probably not necessarily biological(unless mephisto is my father), I could be adopted. I think she has suffered a lot, by losing her brother, vision(not technically dead), I think she needs someone to curb her sadness and cure her resentment.
As you mentioned with Wanda, of course Yelena and Nat’s child would have to be adopted. Or, they could have had a child before their procedure, whilst in the Red Room
