I don't believe in bullying kids about things that are NOT important. I don't want to be a control freak or micro-manage them.
I believe in picking battles, and "letting kids be kids" when it doesn't hurt anything. There are enough rules that must be imposed upon them (and enforced) for the good of their soul, the good of society, and the good of the family.
If I can't charge a given behavior (e.g., "fidgeting") with a violation of one of these Goods, I let them be.
Kids can't be, and shouldn't be, robots. They should also have their individuality respected -- God made each person different.
We accuse the modern SSPX of creating "cookie cutter" phlegmatic priests in Winona, among other things. Why should we be guilty of squashing the same innocent individuality in our own children?
I don't think individuality is an effect of Original Sin. I think it's something God intended for there to be from the beginning.