Impressive!It was a composite! I was really excited about that one! My husband is in surgery fellowship, and that was a co-worker's baby! We are all about safe-photography!!!
SHot #6 has very strong backlight, but the child's face is in rather dim, low, indoor light. It;s not a good lighting pattern for a bright, happy expression--it needs some brightening of the child's face. And as has been mentioned, the focus is off a wee bit on it.
Overall, I think most of these are just a little bit dark, and need a bit more exposure and or brightness added in post processing; the overall look is soft, and low-contrast, which is a look I like, but think they need juuuust a touch more oomph added...maybe tick up the exposure like .7 EV or so on a couple.
The strongest one in processing and subject agreement is the one of the little girl looking down, the sepia tone shot, #4. It's a high-angle, looking-down-at-child shot, which shows her pretty hair and lovely eyelashes, and how cute she is. What parent wouldn't love to see that shot, with five other shots from that play session combined with it?
You have a good mix of camera heights and angles; on photo forums there's way too much over-emphasis on getting down to the child's level; sometimes, much of the time, that's a good idea, but it's far from being a rule one must follow; shot #4 is a good example of how the high camera placement and the downward looking angle can help infantalize the subject, and emphasize the small stature of younger children. Sometimes it's good to be way below the kid's height, to make them loom and look powerful, like when the kid plays in a superhero costume, or climbs a ladder or stands up tall on a set of stairs,etc.
I shot number six today. I had a hard time with him because he was moving around, and that is something I am still practicing. (Shooting kids in motion.) Easy on auto! Learning to do in manual! Haha