I play a lot of tennis and golf and there are some lovely women whom have definitely been caught by their children for odd day childcare.
They are not providing full-time care but the creep on their time has grown.
One joined a golf away social team and used that to carve out one day that she wasn't available, to pained faces from her two daughters when they heard.
Another joined a tennis tournament competition with our club that has her away regularly at the weekend, again to carve out free time.
It is annoying to have lay markers down in your own week, to have free time.
It is why some people love their holidays.
The OP is 100% correct to be mulling this over now, BEFORE she actually retires, because the expectations and entitlement can creep up on you which can make a hard conversation difficult and upsetting for those being told!
So many women are conditioned to keep the peace, that they do it, rather than upset children that are still depending on them so much, despite being adults.
Having young children and juggling work is very busy.
I think it is even more of a shock for young couples if they have had years of travel, holidays, eating out a lot, stags, hens, to suddenly not having that disposable income anymore because of childcare and all the running around involved.
40 years ago not everyone had that pre children lifestyle.
So much easier to manage expectations now before she retires that after when they have gotten comfortable with mum being at the end of the phone.
It is very clear the OP, despite working is already called upon, and it just such grandmothers that can find their lives swallowed up by the expectations of their children without so much as a conversation to check whether or not that was actually how she wanted to spend her retirement.
I agree with the suggestion of writing a bucket list and pin it somewhere that everyone can clock YOUR plans.