My wife (Spaniard, born in Spain) and I (United States

H​i. If they are under 18 you could manage at the closer spanish embassy, their spanish nationality as their rights as spaniars sons. You got all the información at link above ( I put you the translation into english by on web translator )

Option for Spanish nationality for minor. The father or mother may submit the documentation to start the option record for Spanish nationality of the child. The presence of both parents and children is not necessary to open the file. Minor children whose parents have opted for Spanish nationality or recovered are eligible for Spanish nationality:-children under 14 years - for the signing of the Act will require the presence of the father and mother of the / the youngest - children aged 14-18 - signing d the Act will require the presence of father, mother and the child. It requires renunciation of the current nationality of the child, except if he is a national of a Latin American country, Andorra, Philippines, Equatorial Guinea or Portugal.documentacion to submit (original with a photocopy):-literal birth certificate of the / a minor - Literal certificate of birth of the father or of the mother's nationality Spanish.-literal birth certificate of the father or the mother of foreign nationality - certificate of marriage of the parents - Spanish passport of the father and/or the mother of nationality Spanish - current documentation (passport or identity card) the father or the mother's nationality foreign-current valid passport of the / retail - resident card in USA or work permit, or certificate of U.S. naturalization of the father , mother and the / minor - Declaration data sheet completed and signed by the / interested/to.

LINK

http://www.exteriores.gob.es/Consulados/MIAMI/es/ServiciosConsulares/Paginas/SCMiami/Nacionalidad.aspx