I have done presentations on the issue of grandparents raising grandchildren in the past, to groups like the LA City Attorneys Elder Abuse Task Force. I work with the authors of Bet Tzedeks Kinship Care guide. It's an issue that I've had a long involvement with as an advocate of older adults. My stance has always been that it is good for the older adult to provide care, even as the sole caregiver for kids. It may be expensive, and painful, and thankless at times, but they live longer, report better health and are involved in activities known to preserve cognitive skills. It is good for the grandparent.
Now there is a study out of Johns Hopkins school of public health that gives it a whole new flavor. Grandparents who provide care have a better safety record than any other group. Any group. There are half as many injuries to kids with grandparents looking after tham than with day care, preschool, stay at home moms, anyone. Grandparents rule. If injuries seems like a small measure to base it on, you should know that injuries are the leading cause of death for toddlers. With immunizations (don't get me started on that!), kids die less often from infectious disease and they don't have heart disease and such in large numbers. Letting your kids grandparents take care of them may just save two lives. ( For some Moms it may save three!)