My feeling is, if you know for certain, through comments these specific people have made, that they are disturbed by emails at night and don't appreciate them, it's just better from a professional standpoint to not send them emails at night. Why do something that you know will irritate a colleague, when it doesn't really need to be done?
You can try the time delay, saving a draft, emailing it to yourself first, whatever. I don't know what your job is so I don't want to diminish it, but I'm just wondering, if an email doesn't get sent because you went into labor, is it really going to mess everything up? If it really is, perhaps you could make a temporary deal with another co-worker that you will send her the emails as you write them, and then if for some reason you aren't able to send them to the real recipient yourself, she can do it for you.
A friend of mine has chosen to get rid of her landline and uses her cell phone solely. She keeps it on 24/7, by the bed, in case of emergencies. It rings for text messages the same as it does for a phone call. I didn't realize this, but after one too many early morning texts which I thought she could read later at her leisure, she told me about her setup. I didn't know before, so I wasn't rude then; but now that I know, I think I would be rude to text her at a time it's likely to wake her up (for a non-emergency).