The third one is definitely my favorite, however I have a couple of nit-picky things on my mind.
1. Strong vignette, something I've personally started to dislike after having a long period of using them myself. A bit on the darker side for me, including the eyes, something that to me makes the little guy look quite evil. A good concept though I really don't enjoy how high the camera is, forcing you to shoot down at an awkward level for a little child.
I do like the line-work you've incorporated as well as the image manipulation. A little heavy handed for my taste, but a good job (speaking specifically of the colors, tones, and saturation of the image)
2. Vignette again, sorry to bring it up just as I said before something I no longer have taste for anymore. This time you are almost on the same plane as the subject which is a much more flattering angle. Seems you either had a tilt/shift or did some image manipulation to blur out the top of her head, I'm guessing this was image manipulation simply because the blurr seems a bit off to me. Could just be the lens though.
I do like the saturation, and contrast in this photo. Also, love the fact that you realize not every picture of your children needs to be smiling and laughing

This sounds like a small compliment, but on the contrary this is quite big. Just like adults, sometimes things just look better serious! I enjoy the composition as well, a slightly tighter crop could just increase interest slightly but I don't think it is needed.
3. This is one of those times I realize these are spur of the moment shots, but just still want a little more because of the potential! Lovely shot, the only problem is I'm seeing up a little girl's nose. Well that and the other child is in dire need of a reflector to help light her up a bit. Actually, the image is slightly tilted (even if it is technically straight the image feels like it is tilting to the left).
So close to a perfect, truly candid shot, that it makes me just want more. The colors are spot on for the feeling you're pulling out, as well as the complimenting composition. Very nice shot, especially for a family book. Something I wish I had growing up!
Overall, these are nice shots. I understand they are of your family so most likely the highest grade of effort was probably not going into it (we all know that by the time you are shooting loved ones all you want to do is just click the shutter and enjoy their company) So take what I say with a side order of salt.
Can't wait to see some more