Hi long short I have a blended family of 6 kids, his x3 mine x2 only 1 resident and ours baby. I have only just sorted my child arrangements after 4 horrible years. We managed to agree a summer split 2 children together but this year we flipped the weekends as my sister has a destination wedding and it's the complete opposite week and we're all bridesmaids etc. step kids are of course invited. Here's the complication. They stay with us alternate weekends and alternate mon, stays same over breaks only he can da an extra night in the weekend then has the day times instead of evening pick ups I.e takes the working day. 
 

my other half has asked mum is she willing to swap the summer break weekends so ensure we can spend time with the kids together and the right leave from work etc so that they can all come to the wedding week away. Mum is rigid that she won't swap her reasonbeing that I shouldn't of swapped my weekends when he has children? I had no choice as it's my sisters wedding and she of course chose her date. She has no plans in terms of breaks and days out etc and her alternative child care is her mum who is retired. Her partner has no children to accommodate etc. 

my question I guess is how should this be managed without having to go back through drawn out court process. We are trying to make sure the children spend the same anniunt of time with us and also come the wedding for the week. It makes a huge difference in terms of booking tickets and travel on mini bus as opposed to cars etc so I'm in a small panic. I feel ou position is reasonable and though a minor inconvenience has the kids at the forefront.

thanks