Around here, there is a very popular sports team management platform called Spond. While many parents call it a huge chore, it definitely beats the crap out if Facebook groups et al. I've seen people starting to use it more and more for any type of group that wants to organize events, communicate to members etc.

The obvious downside is that (like with other apps) everything is inside a closed ecosystem. But there is zero spam, only a few non-intrusive ads, and generally good UX all around.