1/2 of the couple's children should have extra digits.
Work Step by Step
Let P=polydactyly allele and p=normal allele. To have a normal daughter (pp) with a normal wife (pp), the man must be Pp. That means that the man and his wife make Ppxpp. The Punnett square shows an expected phenotypic ratio among their children of 1:1 Pp:pp or polydactyly:normal phenotypes.