I'm appalled that there aren't all of the appropriate categories like:
mestizo
castizo
cholo
mulatto
zambo
espomolo
morisco
zambiago
cambujo
alvarazado
borquino
Those should definitely be added, oh, and quadroon and octaroon as well. And we would have to come up with all of the possible terms for every possible admixture of races. Let's see, what term can we come up with for a person who is one quarter Indian (subcontinent), one quarter scandinavian, one eighth native American, one eighth Polynesian, one eighth Australian aborigine, and one eighth Persian? What would the child of that person and a person who is one quarter celtic, one quarter african, one quarter arab, and one quarter slavic be called? Wait...did that one quarter African come from Bantu or Khoisan ancestors?
Hrmm, maybe the form would end up being too long. Alternatively, we could just remove the entire question.