Would you announce pregnancy to an ex?

My boyfriend wants to announce our pregnancy to his to ex-wife. He felt that it'd be in his and her best interest she wouldn't hear it from people or Facebook, but rather himself. They are co-parenting their teenage son. I think it would be awkward but respect my boyfriend for being thoughtful. He have such a hard time trying to get on her good side... but she does confide in him when there are difficulties in life (trouble at work, sick parents, etc).

Onto me... I am still friends with my ex-fiance but he's not the best friend. He doesn't follow up with you and will not share any personal details. It's like I'm friends with a stranger every time we meet up (we see each other at least 6 times a year; my boyfriend and his ex wife: ZERO time). So when I found out I was pregnant, naturally and thankfully, I didn't think of him. He hasn't move on but it's very respectful toward our friendship. The first two years though, he hinted about getting back with me, etc.

Should I tell him or just wait until I'm showing? I honestly feel like I don't have to, so I'll rephrase my question: have you told an ex or would you announce it to an ex?

I just don't like telling people things I know they won't enjoy or be happy for me. He definitely won't be happy!