(1) to give advice to the grandchild in what you believe they should be doing?
Depends on the nature of the advice. If for instance the parents have decided that junior has to be a professional violinist, and the grandparent is siding with the kid, that is a good thing. However, if the grandparent is making the same mistake, that will increase pressure on the kid.
or:
(2) enjoy the grandchild and let the parents do their job?
That depends on the qualities of the parents. However, when quality is lacking in the parents, it often seems to be the case that it is lacking in the grandparents as well, or that the parents consider junior as their own scientific experiment on how to screw up a young kid, and do not allow for interference, even if it is completely justified and reasonable

.