In clash, my members used BAND to communicate. It has a main page where you can make posts to the whole group, you can also private message and create public and private chat rooms.
For example, I had a chat room for my leaders (private - they call it direct message but you can rename it and put in as many people as you like) , a private chat for each level, and a public troop request chat if people needed troops and there were no responses in game.
There are also photo albums which you can upload recommended bases at each level or what have you.
Our favorite thing was the poll option (voting when to start war) and the to do list, where people could claim what base they wanted to hit.
You can download BAND on the google play or App Store or access it on pc/Mac as well. If you want more info, hit me up with a pm.
Hope this helps!
Anna