fridaysforfuture, but everyday@SeventhMagpie
If you'd be interested to look at other projects from the fediverse that have solved that issue, there's #hubzilla that does so.
You can create private lists and choose them as to where the content gets distibuted.
You can also choose end2end encryption.
BUT: for really sensitive infos, it's still not the plattform that shall be used.
https://project.hubzilla.org
All Jonkman Microblog content and data are available under the