Honestly?
You can never preempt what will wind up new parents.
They are sleep deprived, hormonal and have no idea what they are doing.
You can't usually guess what they will take personally (and I'm that new parent who fell out with her mum for a week because of a phone call we had three days post birth).
Things I personally would avoid;
Suggesting you should be at the birth
Trying to visit on your terms immediately after the birth (or even within the first week) without an invitation.
Making any comment on their parenting decisions within the first two months (the only right thing to say is "you are doing a great job")
Being in their house and not cooking/cleaning/making yourself useful.
Demanding to hold the baby and being reluctant to give the baby back. (Demanding and not asking).
The very best thing you can do is ask them what they want, and respect the answers even if you don't like them.
The way you are in the first few months can massively shape the entire relationship going forward. If you are respectful of their space, it will likely be repaid in spades by open access to them and your grandchild.
Day 3-4 post birth is the worst time for a women, I have a hormonal breakdown on day three, every single time. That is the day to only be there if you are specifically invited or risk having your head ripped off!
I know the above sounds daunting, but if you heed the advice you will get on this site, it will make your life much better in the long run.
And congratulations on being a gran!