As mentioned, definitely somewhat underexposed. I think a reflector camera left would have helped greatly. In addition, while the choice of background is good, f8 on a 28mm lens is NOT an ideal portrait setting. You have far too much DoF, and the sharply focused background is very distracting. Also, try to avoid cutting off bits of people, such as the feet of the centre subject. Finally, don't forget to level your images.
All of that aside, the poses and the ideas are good, just a little more work on the technical side.
Just my $00.02 worth - your mileage may vary.
~John