Too heavy handed on the post processing, I think. That first one is weird... oversharpened? Not sure. They're also blown out (overexposed) as chris mentioned.
The last one is not overblown but it looks like the saturation was cranked up pretty noticably. Nice colors but didn't look natural for me. Might be a contrast thing, too. Not sure.
Other than the technical comments...
#4 is very cute. Nice picture. #3 is nice, but I think the crop might have been just a bit over-aggressive. Too much of her head cut off IMO.
#1 and #2 I do not care for. Kids sticking their hands in their mouths is not terribly appealing. I instantly think of what that must taste like... what must that kid have had their hands in all day... germs... blech! Might just be a parental reaction, but I don't care for it.
I do really like 4 a lot though. Cute kid, nice facial expresion.