Garment Designer comes with all Standard sizes already built in:
And you can create your own Custom measurements.
For Children it has:
In Garment Designer a Sloper is the green silhoutte that is created when you enter your body measurements - this is an exact replica of your body measurements. The black silhouette is the pattern that you are drafting, Susan put the sloper inside the pattern so that you can see where the pattern is going to land in reference to your body. It makes the guess work a whole lot easier when you are drafting custom designs.
Hope this helps.