not knowing how far into the season you are, but getting kids to gel can be tough.  if you have tried laying down the law and being tough isnt work (this is normally my approach) how about trying something completely different that changes their focus a little and brings some fun into the game.  

parents vs kids game of touch (still keeping up with their fitness at least).  

kids coach the coach (how game are you to take on this?)

maybe a game of beach soccer and some fitness work.  really anything to take them out of their normal training and playing environment and make them work as a team.  

you could also pair up the people that like each other the least and get them to teach the other a skill they think they need to work on, or to get them to work together to come up with an exercise for the whole team to work on and use one each week.  

it might get some dialogue going and help.

good luck.