It’s tricky that’s for sure. I’ve got two main friends, both of whom became grandparents much sooner than me and we all have different circumstances. They certainly did, and sometimes still do, cancel for grandchildren. But, knowing their adult children and the personalities involved, I can see why they do it. They are relied upon. Made to feel guilty if they don’t do it. It’s not that they don’t like me, they do, but the grandchildren take precedence. I’ve two choices: accept it or lose the friendship. I choose to be flexible. I’ve got a grandchild myself and he means everything to me but I am not involved in his care as they live abroad. I’ve no doubt I’d leap into action if they were nearer.
The trick is join clubs, NT, other groups where you will meet more people, like I did, without children, grandchildren, older adult children where the grandkids are teens etc. that way there is no relying on these old friends and you may find that you will be the one struggling to fit them in when they suggest a date!