I don't think that separate PNRs satisfies the rule. Even on separate PNRs, you still have a responsibility to the child. You'll need someone with more customer service policy knowledge for a definitive answer.

My advise would be to select the best available seats right now then try to change them later if you find out that a split PNR would work.

Person lacks ability to adequately impart information orally to other passengers, or person has:

• A condition or responsibilities, such as caring for a small child, that might prevent person from performing one or more applicable functions listed on safety information card