I find the idea of being a grandmother under 60, quite odd. Both my grandmothers were 60 when I was born, my children's grandparents were both about a year short of 60.
DH and I were both 64 and my Dil's mother was 71 when we became grandparents.
No disadvantages that I can see. By the time they came we were retired so free to spend time with DGC, although not living close enough to offer regular support. At nearly 76. I can still hold my own in a kickabout and keep up with DGC, the elder of whom is now in secondary scool