Originally Posted by jmastron

Then if flying a "child" truly saves the airline money, they can offer child discounts, as they did in the past, and/or can fix their system to allow different fares in the same PNR, as all the OP is trying to do is get the lowest total fare available in the same cabin.

I usually select the proper number of "child" entries when booking us together, but end up regretting it as I end up having to click through more screens admonishing that special fares may require identification...even though the fare is exactly the same.

OP -- while the TSA requires birthdates to be entered, for most airlines that's not linked to the ticketing; you should try doing the booking anyway; I suspect it will go through.

IROPS can be an issue, but calling to have the itineraries linked by note (which doesn't guarantee automatically being rebooked together) and having a small child standing there who obviously must travel with you will get you put together (possibly on a later flight).