Originally Posted by
looper33
I know Norwegian doesn't. If they really want my 7 year old sitting alone.. well good luck with that

Um, I think you summed it up.
I believe an airline has to participate in Global Entry (and PreCheck), though I could be wrong about that. I'd be VERY surprised if there was a way to enter your number, but having a physical card may allow you to use GE at US airport.
Methinks you are getting what you paid for
Not trying to be snarky, just an observation .... what you take for granted is used by airline to cut costs @:-)