Totally agree, this is one battle you should not attend.
We all have to learn from our mistakes.
Thinking back to when I first learned to sew... to be honest, I was not interested in cutting the pattern "thread perfect" as our teacher wanted. All I was going for was a finished product. The 1st quilt I made... I was just making. Now I shoot for things/patterns a bit more complicated. It's a learning process and your girls will learn. In the mean time, you've taught them another skill.