I remember the days when one of my little boys would streak through the livingroom after bathtime, naked and without a thought about it. As a toddler, he had no sense of modesty whatsoever, as should be expected from a little one.
Over time, he became aware of what nakedness is and started to keep himself covered up. He realized (with little help from us) the inherent shame of being naked, and actually preferred to cover his body. I thank God for it, because we learn from the Garden of Eden that it is right and proper to cover ourselves in this fallen world.
Ah, the slow awakening of a child's conscience! It is the parent's help in raising them to be God-fearing and holy (set-apart). We should never, ever violate that sense of modesty by dressing them in skimpy clothes because it's "cute" or because the weather's hot.
But whoso shall offend one of these little ones which believe in me, it were better for him that a millstone were hanged about his neck, and that he were drowned in the depth of the sea. (Matthew 18:6)
That word "offend" doesn't mean what people think it means. It does not mean to cause vexation or annoyance. Here it means to entrap, scandalize, entice to sin. To offend a little one means to train him/her to sin!
Let us consider Biblical guidelines for modesty when dressing our littlest ones, too.