My MIL is... a very unique individual. She had him when she was 15, then divorced his dad when she 22 and left him.

She's still super immature, and I'm not about her in my life except a few pleasantries here and there.

The complicated relationship has me wondering, when that time comes, how do I even tell her? I don't have her number and only thing I can do is shoot her a msg on Facebook like, "Hey, you're 38 and going to be a grandma!"

Despite my distance I still feel as if that's a bit informal.

Does it seem informal to you? I just want things to be planned out way ahead of time since we are not really actively using BC now. Lol