There's always a possibility of having issues during IRROPS that way. I recommend trying to be on the same PNR whenever easily doable.
Valid point.
Although IMHO Korean requirements don't classify as "easily doable" due to the paperwork required.
IINM the documentation needed is:
A) Marriage certificate to prove you're married.
B) Birth certificate to prove its your kid.
C) Passports or drivers license for everybody to confirm names and date of birth.
D) Create individual accounts for each passenger.
E) Fill out a form with the account info for everybody (and some other basic information) requesting to link the accounts for redemption (and share miles if necessary).
The good thing is, you can put KE awards on hold while dealing with all that stuff.