You each made a gift of equity of jointly owned property to two separate people....half to your son and half to your daughter-in-law if they're both on the deed with equal shares.
The 709 has to list each one of them because the transfer was to more than one person. So, you'd have a one line with your son as donee and another with your daughter-in-law as donee.....you can't put them both on the same line in Schedule A.
