I thought I’d add that Daz Studio 4.5 has a neat little feature regarding the Genesis models which some newer people might not have noticed. If you’re using Genesis models (and you should be if you’re using Daz, it’s arguably the BEST feature yet) you can actually import much of the clothing items from the Mk. 4 range like Kids 4 or Victoria 4 and it will auto-fit and convert it for the model you’re using.
Simply scale your Genesis character to the correct size and shape then add the clothing and watch it automatically shrink or expand to fit. The beauty of this is you can use virtually any clothing on the model, even ones intended for other characters. I had a pretty dress for Victoria 4 which I was able to get working on a teenage Genesis character perfectly fine.
If you’re looking to expand your wardrobe for child characters, look at the wealth of K4 outfits already available, though as yet I don’t think morphs function so adding character morphs such as Kaelyn probably won’t work.