AITA for not changing my custody schedule to accommodate my ex’s dying father?

My ex is extremely close with her father. He’s an amazing man who raised her on his own. When we were married, he lived with us and we really bonded. Together, my ex and I have two children, 7 and 5. We divorced 2 years ago. Our custody schedule is I get the kids every other weekend, one day a week, alternate holidays, etc.

My ex-FIL is dying of cancer. There’s no official prognosis but he likely won’t live past summer. He’s receiving hospice in my ex’s home. He’s not bedridden yet but is pretty weak, The kids and her are naturally devastated.

My ex invited me to coffee a few days ago and said she had a huge favor to ask. She wants me to not take the kids on the weekends and allow all holidays to take place at her house until FIL dies, so they don’t miss out on time. She explained I could still visit on the weekends and hang out with them, but it’d be at their house.

I said absolutely not. I’m willing to celebrate holidays and birthdays together, that’s not unreasonable. But I won’t just see my kids for a few hours on the weekends.

Legally, my ex cannot enforce this. We have a court order. I could choose to allow it, but I’m saying no. She began to cry and begged me. I said the kids are with them 6 days a week when I don’t have them on weekends. I pointed out the kids should also get respite from having to deal with their grandfather’s cancer.

My ex called me selfish and unkind. I spoke with my mother who feels I should at least give up my one day a week with them, but that’d mean I only see my kids twice a month. I feel losing their dad while also losing their grandparent that raised them will be traumatic. Plus, they’re young but they will likely remember I abandoned them during this time and not understand why I listened to their mother.

AITA?