Is there software that allows me to send bot campaigns to FB closed group members?
Not sure if this is possible.
I think you can only send messages on FB messenger only to the users, who have opted for it by iniitiating the interaction with your bot or on your page.
It would be cool if we had parameters in the bot that could refer to FB user IDs to display info (like their name), and use a post link to the bot instead of a messenger bot. Or part of the groups documentation could have a bot with the community rules, agreement to the rules, etc.