IL's have the 2 dcs once a week for me to work. I am very grateful for this, always take them and pick them up on time, always say thank you for having them and dont really ask for any extra childcare (or very rarely).
Yesterday I picked up dcs and asked if they could do 2 days next week because I am taking my mum to see a show for her birthday. I am doing it in the shortest time possible (driving 3 hours to mums, then an hour to show, then staying over, then driving mum back home, then 3 hours home for me). They said ok.
Then this morning I had a txt saying 'you will have to find someone else for next week, please dont take us for granted in future' 
I was initially really cross, but am now just upset that this txt will now cause bad feeling between us. DH has spoken to FIL and FIL says they love having the dcs but they didnt like that I had planned something and then asked them, if I had asked them before and then planned it they would be ok with it 
So now I dont think I can take my mum away next week, not because the IL's are doing anything, but just because I didnt ask them the right way round!