بسم الله الرحمن الرحیم
First of all I should mention that the boy’s wali (his father) doesn’t seem to be related to that matter as Mrs. Bleeding Fingers said. (as you inquired):
Has divorce taken place or does it require signatures of the boy's
wali i.e. his father?
Meanwhile, you’d better pay attention to some related terms of divorce or Talaq briefly as well (as some of Talaq terms):
- In Talaq or divorce, its terms ought to be done entirely, not some
parts of that.
- The Siqag of Talaq ought to be read (as a significant terms of Talaq)
- The Siqah of Talaq ought to be recite (by the tongue), hence it won’t
be valid to write on the paper
Otherwise, (I presume) the divorce apparently won’t be correct.