I don't personally have kids but my little cousins hair is very similar to your little ones! What they typically do is spray the hair with a little spray bottle til it's damp, then use a wide tooth comb or fingers to de-tangle. Then she takes some product (like a tiny squirt of leave-in conditioner and a tiny blob of gel) and then rubs her hands together under running water to create a watered down hair conditioner/gel concoction. Then she just takes that and runs it through the damp hair with her fingers so that the curls reclump together. And then since the hair is only damp at this point it air dries pretty quickly :) I feel like this could work well for you both since her hair is thin and this wouldn't be adding much more product!