Don't worry about it, just book the tickets. You can deal with the "accompanied" issue as late as the gate in a pinch (but preferably at the check-in counter or lounge).
AA does not require or expect that children be on the same PNR and the adult could be anyone, not even a relative.
While AA can place a note in the PNR notes for each passenger and that is all "linking" does, it is of no value in this situation as the GA will still need to see both of you at the gate and assure that you physically board if the child does.