Oh bleugh! Sounds like it feels really crap. I hope you figure out what to do to help the sitation and that you cagey yhe chance to talk to DH and get him on board. It reminds me of a work sitation recently where they discussed how when you have even just 1 new person in the group it becomes a new 'team' and you have to act as such. All the team process that occur with the creation of a new group apply and as such the 'leader' needs to put in dynamics procedure and policies and create a new culture. Maybe thats a way of looking at it. I know you are just venting so ignore my advice if you want. But I wonder if actually talking about 'the elephant in the room' may open up the discussion for everyone and maybe the kids themselves will have suggestions of how to make it all better?

Good luck. I hate being a step mum. But if I'm gunna do it- I'm gunna do it right