As other posters have said, don't assume anything, say you would like to help and then ASK your DIL and son what would be the most useful thing you could do. It may not be that same from one week to the next. Don't overstay on your visits, don't visit too often (how often is too often is an individual matter, be sensitive to that) and, very, very, importantly, don't give advice unless you are asked.
If you are asked about an aspect of baby care you could say something like "in my day we did X but it may be different now, what does your maternal nurse/advisor say about this?" GN is overflowing with the lamentations of Grans who just can't seem to "zip the lip" as one poster succinctly put it.
Apart from all the "dont's" the most important "do" is to relax and enjoy the wonder of holding your grandchild in your arms and loving every precious moment. It is life affirming itself in one tiny bundle.
How do you acknowledge Easter.
Is there anyone who still thinks that Israel's actions in Gaza are justifiable?