Circling back on this. Just flew the outbound. I had booked my child as an adult with my DOB and it was fixed at check in. My son is booked on a return in January and I have a separate PNR on that flight as well. My problem now is that I want to change my return from this trip (next week) and am getting an error message on united.com that I can’t separate from a minor. So I assume my booking is now linked to his despite the fact that the return of this booking is solo? I’ll call 1K but what should I ask them to do especially if I get an unknowledgeable agent?