I guess the thing I fear the most is us coming to a heated argument at one point: his other grandmother's big annual feast is coming up, and his parents always make an appearance. Are we supposed to just ignore them when we arrive? What if they suddenly pretend they're taking an interest and try to interact with baby?
I mean, there's going to be events where we're going to bump into each other eventually. What exactly is socially correct in those kinds of situations?
I don't think that Ignoring is the solution. That could probably perceived by others (on that gathering) as rude, but being cooly polite, as others already mentioned, could do the trick.
If MIL comes over and pretends that everything is fine and suddenly is interrested in you, DH and the baby, then you could suddenly need to get something from another room, or wish to speak with a relative that you haven't seen in a while. There is always a way to excuse yourself from their presence.
If they want to hold or interact with the baby, then maybe baby suddenly needs a diaper change, needs feeding or needs some sleep.
And I can already see his other grandmother (his dad's mother) showing up in the hospital, asking where her own son is, and have it ruin her day to find out how he's been behaving. But short of keeping silent or lying, I don't see how we can fix this.
Others have already put it so well.
It is not your job of fixing it.
On the question of how to contact them/if to contact them at all when baby is born.
I wouldn't. They chose to do the cut direct knowing very well that they'd be grandparents.
To me the cut direct also involves loosing the privilege of knowing what goes on in your lives. That involves knowing when the baby is born.
Just concentrate on the familymembers that are interrested and that are a positive influence in your, and your childs life.