You can put the reservation in your son's (or other's ) name as lead name. The reservation will actually remain in your
DVC account until arrival and can be changed or canceled only by you until that time. Once you make the reservation, give the reservation number (and likely a copy of the reservation) to your son and he can then use that number to set up the reservation in his MyDisneyExperience account. Just note that whatever names you put in the DVC reservation must be the same exact names that are in the
MDE account.
Also note, that if you initially make the reservation with you as the lead, you will need to call MS to change the lead. Any other named guests can be changed via modification online.