Availability, attendance and selection answer different questions. A player may be available on Saturday without being selected, and missing a training session should not automatically change a confirmed team sheet.
An app could keep those records connected while showing coaches an accurate picture. Players would respond against individual sessions or fixtures, coaches would prepare selection privately, and an authorised person would release the final team information. Any formal submission requirements need to be checked separately.
Start with one squad and agree who can see comments about absence or injury. Test late changes, players covering different teams and a cancelled training session. The system should make the current position clear without exposing private coaching discussions or confusing a provisional team with the final announcement.
Related reading: Membership and Club Management Software.