mom2eight nailed it on the "snapshots" look. these are underexposed a little bit, and are cute cause they are of your kids, but portraiture, it is not. The comforters in the first picture are distracting, and the odd tilt on the second one is the same. the lighting is actually pretty bad, cause i can see harsh shadows and and very very flat. A way to fix this is to eventually invest in some sort of hotshoe mounted flash or off camera strobe. maybe even shoot with no flash at all if you have fast enough lenses.
Great looking kids though and I hope they will continue to be so willing as you grow with your photography.