Paul56

I suspect the OP will be going through several airlines as they
discover rambunctious rug rats fly not only Korean but all the
other airlines as well.

Buying an extra seat should not raise your expectation that
the flight will be comfortable in all respects. It only means
that seat will be empty... nothing more nothing less.

I have low expectations when flying simply because much of
the experience is out of my control; however, my reaction is
well within my control... I can chose to have a bad day or to
make the best of it and enjoy myself.