You can disconnect while staying connected on your own terms.
Convincing - tried it with just my partner first and smoothed out some rough edges. I then sent a group email to extended family that included a brief justification, some screen shots of it in action, a picture of the actual server, and an offer to create an account for them. Transparency, ease of use, and privacy were all important factors.
Most live far away and have griped about various facets of Facebook but felt like it was a necessary evil. This has been a good alternative for daily communication, discussions about weather and children, and so forth. The closest to game support is sharing crossword solving times with a hashtag.
Does Mastodon have anything similar?
Event Invitations is one of the few uses of FB that I still have. I'm open to alternatives that simplify facilitate threaded discussions between those who were invited, but as with any system convenience is a factor.
Google Calendar does work, yet somehow (and ironically) seems more intrusive than Facebook in that you're communicating directly with emails; the younger the participant, the greater the lack of enthusiasm for emails.