Oh that’s so unfair on you. I’ll bet you’re already torn in two visiting your mum and juggling childcare! I bet you wish you could do more for your mum and at the same time wish you could help look after grandkids more. Having a grandparent available to look after a child is such a privilege. My husband and I have a parent each, my dad has mixed dementia and needs to be in a home now, my MIL looks after our 18 month old virtually full time. Every waking moment I can’t believe how lucky I am that, I have a MIL so readily available and happy to have my little boy. But if she said to me she can’t have him because she wants to do her nails/get her hair done, sit on her bum and do nothing, I think that’s her right. At the end of the day, my son is my responsibility, If I have to take him to my dads appointments, take him to view care homes etc, I’m going just have to manage. As for your son, I am sympathetic, It’s flipping hard looking after children in this modern world, we don’t have the support network that my parents generation had, family And friends never live nearby and we all work so many hours. I can get why your son might feel disappointed that you can’t look after his kids, but he shouldn’t expect it and should reflect on how lucky he is if you are ever available to look after them.