Every game, and every training, we ask people to set their attendances. And this information is then collated and shown to you in a super simple way.
Just find the game ( via the schedule, or under your team ), and you'll see something like the following.
Every game, every training has a similar view. In the example above, we can see that there are 3 people coming to the game - myself, Robert and Sally. You can see straight away that we have zero people who cannot play - that's the 0 in the red circle. If we had some 'unknowns' - then you'd see a yellow circle too. Just touch the green, yellow or red circles to see who's coming, who's unknown and who can't make it. Couldn't get any easier.
You might also note - that I've listed a comment against my attendance. Traffic can be tough that time of day - so I'm letting the coach know I could be up to 5 minutes late.