If this went to court, the court would probably order in favour of the ex re shifts etc and not necessarily having set days. The logic for childcare would be that if the ex is claiming it via tax credits, that of the 30% owed left, that he pays 2/5 of that to account for the 2/5 days he does work
I just wanted to chime in because I have direct experience of court with regards to shift work and childcare costs with my ex.
It may be different because I’m the RP but my ex worked shifts which changed week to week, said he wanted 50:50 but couldn’t do set days.
I worked part time at the time and my complaint was that i couldn’t up my hours and work full time to enable the 50:50 care because of my ex’s shift patterns or make any plans further than 2 weeks in advance.
I also had to pay for full time childcare even though I didn’t require it because I didn’t know from week to week which days my ex would be having our son and I couldn’t find anywhere that could do childcare on an ad hoc basis.
My income and our lives were greatly limited by my ex and his unreasonable work pattern and him insisting on doing 50:50 even though he couldn’t really adhere to it.
His view of 50:50 was having our DS to sleep at his house 3-4 nights a week but the reality was he would collect our toddler at 6.30pm after work, put him to bed at his house then drop him home at 6.30.
The court ruling was that I was able to keep residency of our DS and I could enforce set days for my ex. He couldn’t in reality stick to 50:50 (he never really had this) and when he protested about the arrangement changing the judge actually said
“Your long standing work pattern is not of concern here, MsSpongebob had to change her job to be able to support her children and be available to care for them which is what I also suggest you do”.
Set days were issued for contact and all I had to do was make sure my DS was available but if my ex couldn’t make it then tough luck for him.
In the end we’ve fallen into a regularly pattern of Weds and EOW plus as much extra in the school holidays as my ex is available to do.
I work full time and I have to pay ALL of the childcare bill because my ex now pays maintenance and not a penny more. The courts will not generally rule for a NRP to pay for childcare unless it falls directly on their usual access day.
I honestly think in the OP’s DP’s situation he and the children would be better off with him being the RP if the mum’s shift pattern is ever changing and her having the kids whenever she is able but that way Dad is still available for all the emergencies, school runs etc due to being part time but he’d then be able to be financially supported to do that.
Or he pushes for set contact days like I did and mum sorts out childcare for the kids if her work falls on her days, DP sorts childcare for his set days and then he can then work fall time and no one is being disadvantaged financially.