As regards your son's DNA.
Each person's DNA is connected to their profile. His DNA must be attached to his profile. Due to DNA privacy laws, he must create his own WikiTree profile, if he does not have one. He must add his DNA to his profile.
He does not need to be active in WikiTree, after he completes the first two steps, as long as he adds you to his trusted list so you can maintain his profile and see the results of his DNA matches.
Just thought of another suggestion. Since he will need to use his e-mail (WikiTree limits an e-mail to one profile. Living people require and e-mail address), set up a rule in his e-mail to forward e-mails from WikiTree to you.