All DNA test information needs to be entered on the profile of the test taker himself or herself. For privacy reasons, if the test taker is living, he will need to enter the DNA test information himself. You should create profiles for the son and the grandson. Then on each of their profiles, on their 'edit' page, just below the entry for 'gender' enter the person's e-mail address. WikiTree will send an invitation to him to join WikiTree. Each one should join, and add his own yDNA test information. Then, if he chooses, he can make you the manager of his profile.