Thoughts per req:
1. This is a situation where, if you needed to pose him in the tree's shadow (I would recommend a different location) you should have used spot metering. The subject is at least a full stop under-exposed. Additionally the posed and expression are rather awkward. Also, consider your backgrounds; you've made good use of selective focus, but there's so many different colours, textures and brightness levels that it's very distracting.
2. Nice! I think this is well done. I like the exposure here, I suspect it may show as about 1/3 - 1/2 stop under, but no matter, it works well IMO. The only issue is that the face seems slightly soft, but I think that is a compression issue from your hosting 'site.
3. Nice interplay of light and and shadow on the face; it works very well, but again an awkward pose and the position of the hands really doesn't work.
4. A nice 'happy child playing shot'. Good exposure here - it just needs to be leveled.
Just my $00.02 worth - your mileage may vary.
~John