Good thinking, it's prolly what I'd end up doing as well.
What made the difference I think was that my BIL was brave enough to show up at the hospital and sincerely congratulate DH...i think my DH knew that took a lot of 'face' to do and he appreciated it.

Just occured to me as well it's a great thing you're doing keeping in touch with your SIL on a regular basis because then when she's about due or has any news (or if you haven't heard from her or BIL) it won't look out of the ordinary if you were to "pop by" or text to see how things are going...that way you can get in early for the congratulatory celebration in case MIL or BIL forget to message you about the birth (and is easier to go to hospital rather than wait for an invite to the house)...sorry if it sounds like my imagination is running away with me here!

I just also am aware of how important it is to keep relationships going for the little ones' sake as I didn't have that when I was growing up.

and BTW love the update on the current wardrobe for your DD! what a good match! love it! fashionista you've got there!