I have 6 grandchildren with a wide age-range.
With my older two GC, I shared childcare with the other GPs. I was divorced and working part-time.
Then, my youngest son had his first baby They asked if I could share child care and nursery pick ups etc when d.I.l. returned to work. I had to decline because I was already committed to my older two . Had I agreed , I would have had no time at all for myself. But I said I would definitely help out with babysitting, if they wanted an evening out etc. I felt no guilt. And I knew, if it came to that, they could easily afford outside childcare. It has worked out fine.
My middle son chose not to involve me in childcare. His wife is an only child and they preferred to have her mother (10 years younger than me) for regular childcare.
I hope it all works out for you .