I'm simultaneously surprised and not surprised by the issues you had.

As mentioned previously, airline reservation systems are still an archaic setup when it comes to PNRs and Ticketing. The booking of segments is totally different than the actual ticket. It just so happens that now, E-Tickets make this distinction basically invisible to the public.

The DL agent would have been able to change the name field of the PNR in 2 seconds. What would happen, however, is that the ETKT previously associated with that name field would disassociate since the name fields wouldn't match. (The same is generally true with a segment change or a class of service change... SABRE would automatically synch up a same day flight or class of service change as long as the city pairs remained unchanged. Changing the date, routing or number of segments would require a reissue).

Since the booking and the ticket are separate, all delta would have to have done is void or refund the ticket associated with the name field of your son while not touching the actual segments, change the name field, price the itinerary (would have been the same number of miles since you are holding the same booking class as you previously did), and issue a ticket.

Since this would not create a new PNR (unless the original one was split), there *might* be a breakdown between DL and VA's system since VA's system might not understand that the only thing that was changed was the name by the OAL PNR. Nevertheless, they would be able to see the new ticket number with valid flight coupons that they would manually integrate into a new PNR or force associate with the already existing PNR.

In 2005, I had a similar situation in an IRROPs with a passenger (I was a ticketing agent) who was allowed to travel on US despite the fact that his secretary booked the ticket in her name. This was on his return segments. The name in the PNR was changed as described above, but the ticket was never reissued. The agents on the outbound simply printed the ticket to paper coupons. When I reissued the ticket for delta flights, the ticket came across in the secretary's name while the PNR was in his. DL obviously wouldn't accept this, so we hand wrote a FIM. Nevertheless, this mismatched issue would have been avoided by issuing a new ticket in the changed name.

Glad it all worked out.