I know it’s an easy answer ‘just say no’ but that doesn’t take into account the guilt I feel for not stepping in.
When we split two years ago ex insisted on 50/50, consequently kids spend a week there and a week here. Recently DD12 has started ‘being ill’ on her weeks with Dad but instead of him sucking it up, being the baddie and either sending her to school or taking time off with her, he’ll text me with ‘DD is saying she’s not well but I’ve got stuff on at work’ and expect me to pick her up (I WFH) and care for her for the day. I know if I say no he’ll tell her that I ‘refused’ to have her so she’ll have to go to school. There have been a couple of times in the past where he’s just gone into work anyway and left her by herself all day and we had words about that not being acceptable. So now he expects me to deal with it when it happens.
If I responded with ‘She’s just going to have to go to school, give her some meds and take her’ he will turn it into ‘So sorry darling but [mean old] mum says you have to go to school’! For what it’s worth she rarely misses a day of school on her weeks with me, she has some great friends and is doing well at school. Why does he not want the responsibility?