Who’s shooting and when?

At our club we have numerous outdoor shooting opportunities throughout the week and no set times through the day therefore it can be hit or miss that when you turn up at the field that you are the only archer. Our club has a policy of minimum of two members to allow you to shoot so can be frustrating when you have to wait.
We want to use social media to communicate or an app to let all members know when they intend to shoot on each day so others can plan their shooting times.
Any suggestions of what your club uses?