A grandparent moving in to provide childcare, rationally, does not make sense.
Let's talk numbers-
Let's say gm moves in for 2 months- 1344 hours of cohabitation (24 hours for 7 days for 8 weeks)
She will provide childcare for 2 days -128 hours (8 hrs×2 days a week for 8 weeks)
Her childcare to cohabitation ratio is 9.52% of childcare vs 90.47% of gm living together without providing childcare
If anybody thinks these numbers make sense, you are in deep denial of your ulterior motives- you want to see your gc, adult children, you feel lonely, you want to be useful
I am of course ignoring the risks.
What if gm gets sick? Then the mother, who "needs" childcare for 2 days, has to to take care of gm, kids and worry about working from home
If her employer is not being reasonable, the worker needs to fix it.
Your adult children are adults. Stop coming to their rescue. They can do it even though it is hard