VioletSky
I would honestly say, be there for the parents. Come when you are asked to visit, put them first, bring food, offer practical help around the house...
The rest, just follow their lead, I'm sure any time they ask you to look after your grandchild they will give instructions... As long as you follow them I can't see anything going wrong really.
Huge amounts haven't changed honestly. Safe sleeping is a priority. Don't offer solids until 6 months. Some things like cot bumpers no longer get used as often. The rest is still quite individual like dummies and breastfeeding/formula, baby led weaning or pre made foods etc. Nothing huge that I am aware of
My first baby is 50 this year, he was a very hungry baby and I was advised to start him on baby rice at 10 days old. He ended up with a very robust digestion until a swim in the Ganges resulted in giardia. He was never fussy over food and ate whatever was put in front of him.
Safe sleeping advice at the time was to lay them on their fronts.
By the time I had my fourth 15 years later things changed with respect to sleeping position, lay them on their backs. Also no solids till 4 months, she turned out to be incredibly fussy over food.
So I think advice does change and I think all parents should go by instinct and what seems best for their own child, and any baby minding grandparents should do what is asked of them.