Being a grandma who also lives with pain I totally feel your frustration. I tend to get frustrated with my daughter because I am the only person she will leave my grandson with. I understand that she is overly protective as she lost her first child at birth and almost lost my grandson at birth also.
I try very hard to understand this and I do but there are times that I just do not feel up to having him here all day and all night. He is a very early riser and I usually do not really get to sleep till around 4 am. It is getting a little easier as he gets older ( he is 6 ). I have not sit him down and tried to explain my health issues yet but he is starting to understand that sometimes Mam-ma’s back and neck hurts really bad and I just cannot get down in the floor with him or play with him for hours.
Over the summer we made our extra room into a bedroom for him and moved all his toys in there. My hope was that he would spend some time in his room playing and that would make it easier on me. However all of our bedrooms are upstairs and while he does go up and play, he doesn’t play long, he brings his toys downstairs to play which is totally fine other than once he gets down here he wants me to play too.
It is hard being a grandparent in pain. We want to spend all the time in the world with our special little ones but it just cannot be done. When your grandchildren wants to stay overnight then your son should be the one taking the lead on their care, feeding and getting up with them in the mornings. Is there a reason he doesn’t?
I feel you should talk to the kids, the 8 year old will be able to understand things easier and better then the 5 year old but hopefully this will make your time with them easier and less frustrating on everyone.
Best of luck