If he is a Wyandotte Sex-link then he is a hybrid, not a true Wyandotte. (Unless, both parents were Wyandottes. However, most sex-links aren't crosses of the same breed.) Sex-Links do not breed true, so offspring may vary. What exactly is your goal for the chicks? Are you trying to create the same color, or another? If you want to produce the same color (Buff Columbian) then I would suggest looking for some Buff Columbian hens or Buff Hens.