The last photography class I had was years ago, but here's my 2 cents.
I like the first one. Try and avoid cropping out the body when it's a focal point. In the first pic it's understandable not getting in all their legs, feet, etc. as they are standing up. In the other two my eyes just seem to expect to see everything since it's close as they are sitting.
Watch how you frame the focal point. In the first one it looks good with them to the left of the stream... make sure there's no trees growing out of the back of their heads though.
