Unfortunately my sister does the same.We. Live hundreds of miles apart,and when I visit I love to meet her grandchildren,but it’s not the first time that a planned trip out has turned into an all day evening babysitting,as my niece needs a break. We usually arrange a bit of shopping and lunch,but then spend all of the time looking for somewhere we can get a buggy into, and then seeing to the baby’s needs,and all the time discussing all of her grandchildren’s teething potty training ,How well they are doing at school etc. Then she is pinging messages back and forth to her daughter,about the children.
I also have gc but unless it was an emergency,I wouldn’t take them on a planned day out,I always babysit when asked and love spending quality time with them,but would feel that it would be wrong to expect someone else to feel the same about my Gc. I have stopped planning trips with my sister as I do find it difficult and now I pop in for a coffee and a chat which is a shame,but even telephone calls are all about her daughter and gc.