Okay, I'm not going to comment on how you can "fix" your current photos, as I am a great believer in getting it right in camera. Of course PS is a great tool and should be used, but it is there to enhance an already good/great photo.
Anyway, I think that you were asking about techniques to take better photos, not how to fix these particular ones?
1. Rule of thirds - get the person/eyes to correspond with the rule of thirds. It makes a HUGE difference.
2. Shallow depth of field (DOF) in order for your subject to really stand out. I shoot around f1.8 to 2.2 most of the time when I take photos of people with a fixed focal (I usually use a 50mm 1.4 for children's portraiture.
3. Shutter speed: nothing under 1/125 for me personally..... Even a bit faster if possible.
4. Check your backgrounds.... make sure you don't have funny things running through/growing out of your subjects' heads (your photo #3 is a prime example of this - see how the wire is cutting her head in half?)
5. Focus should be slap bam on the eyes. This is probably the hardest thing to get right when you start photographing people. Harder when you shoot wider open.
If you can, choose your own focal point rather than letting the camera choose it for you. Focus in the corner (closest to the nose) of the eye. Not on the bridge of the nose.
6. Watch for cropped limbs - in your last photo you have chopped off her hands at the wrists and it looks like it has been amputated. If you crop limbs do not crop them at the joints.
7. Interaction is really, really important: either between the viewer and the subject (through the photographer) in other words eye contact with the camera or else some interaction with the environment. Only rarely does a far-off look out of the photo when no-body knows where the subject is looking, work.
8. Shooting in open shade is best (not dappled) or learn to shoot in full sun so that there aren't distracting shadows on your subject. Overcast days are GREAT, but then you have to look out for flat lighting.
Okay: Now, on applying these to your photos:
#1: Cute! It would have had more "oomph" if you had a "prop" to explain the outfit. In other words if it is a Halloween costume, a pumpkin or something would have helped tell the story.... There is a reason why so many photographers use baskets etc. for babies this age: it is to keeps them contained LOL!
Would look much better if you have shot it using the rule of 1/3rds, but that you can achieve by cropping in PS.
I love the catchlights in her eyes! Nothing like GREAT catchlights! Love her looking at you. Her expression is a bit "blah" BUT if this is an expression that she often has and that is part of her, then capturing it is lovely.
#2 Composition is better. Less dead space above her head would be good and I wish there were a little more space photo right. Even the greater DOF isn't that distracting as it tells something about where you were at and what you were doing (this would not have been the case, if it was supposed to be children's portraiture but for a family album, I think it tells something of the story). Can you see that her eyes are not sharp? In fact the whole photo looks a bit hazy. I think with a slight USM in PS it would look better.
#3 The shadows on her face, neck, shoulders are bothering me, the line through her head is really distracting, for this photo you could clone it out. There is also no eye-contact, so she just looks like she actually wants to be somewhere else (wherever she is looking).
You have a GORGEOUS subject and kudos to you for asking how to improve your photography! Once you start shootkng keeping a couple of the techniques in mind, you photos will really improve! Just don't forget to sometimes shoot your little one just for the fun and for record shots - not everything has to be perfect!
HTH
Anelle