Good character establishment, second half not so great

The first half was really good, the kids were great, most of the characters were grounded, convincing and invest-able. The second half dragged a bit in comparison, bowed down to predictable melodrama and some of the supporting characters just didn't amount to anything...they didn't make enough of the gang of bad guys, what were they doing the whole time after being introduced? They hardly made an impression on the story until they all re-materialised for the shoot-out (during which they were inept in a very disappointing "faceless goons queuing up to get shot" type way) and how come they didn't see the Ellis kid going back and forth to the girls motel room multiple times, I thought they were supposed to be watching her 24/7? Surely they would have cottoned-on that the kids were deeply involved if they actually had been staking-out the girl. Aaaaaaand, the story (or Mud at least) made a big thing of how "evil" the ringleader father was so I was really hoping to see something come of that but he only had a couple of very minor non-descript scenes. Entertaining enough movie over-all though.