Mother, mother in law and grandkids

Hi everyone!
My mother and my mother in law want to be with my kids as much as possible, when we visit our hometown. They ask when they are spending time with the kids. I try to spend time with both, but I feel more confortable when we are staying with my mother. We normally spend more time with my mother.
Last Christmas, I had an appointment in the city where I live and work, and had to leave the kids in hometown:
C- My mother told me that it was fair for her to keep the kids, as the following week we were going to travel with the in laws for 4 days
T- My mother is putting pressure on me so that she can enjoy the kids, as she thinks it is fair. She shouldn`t do that because she normally gets to be more time with the kids and she should be aware that I try to benefit her, even if it means the in laws getting less time with the kids
F- Angry, not understood
A- Tell my mother what I think, that when they fight for the kids, I don’t want to visit hometown
R- My mother says she meant no trouble

Then I felt guilty for having hurt my mother:
C- My mother says she meant no trouble
T- I have hurt her feelings
F- Guilty
A- Explain to her how I feel and ask her to recall her experience with her in laws and having kids
R- We are closer

I see what I did wrong, having a manual for my mother, expecting things from her, and also blaming her for me feeling guilt. But when I told her: -please don’t ask for the kids, I’m doing my best-, I had the feeling I was setting a boundary that I needed. I guess I didn’t do it properly, because I didn’t say, if you ask for the kids, I will do whatever. And I can’t get rid of the thought that it would make me feel guilty, because of the boundary (that I think would hurt her). I guess the easy thing would be letting my mother say whatever she wants about getting the kids and just ignore it, meaning not reacting to it. And believe I won’t be responsible for what she feels.