When my kids started having kids, I said “You can always ask for my help with childcare as long as I can always say ‘No.’”. This has worked out well. They are very respectful of my limitations, and I can enjoy my grandkids without feeling obligated. I help when I can, and sign up for one or two days a week, usually. But I’ve waited my whole life for the freedom of retirement, and plan to enjoy it. Plus I watched my sister raise her grandchildren, and I know the stress of that was one of the factors in her death. These grandparents need to be clear, and they need to respect their own limits. (It’s hard sometimes because you don’t want to fracture the relationship with your grown children, but in the end it is more respectful to set clear boundaries and enforce them.). My six cents.