You did a fantastic job varying the facial features on the two girls. This is a wonderful first attempt!
As for critiquing... It depends on what tools you are using and what look you are going for, but I definitely agree on the previous comments to use a brush with a higher opacity. You could do this simply to lay down the base colors and then work with the brush on the settings you used for this to do blush, blended shading, and many other things. If you are able, sometimes, in order to go for a pale/barely there look with colors, it is better to do everything with a solid brush and then lower the opacity on the layer instead of the colors themselves.
Don't be afraid to go back over and deepen lines that get blended in during the process of the image itself; it will add depth and get rid of some of the uncertainty that other artists might pick up from from the mix-matched lines.
Seriously, though, these two look gorgeous already. smile