You are putting your availability down for the whole day and for all matches - if you say you are available, then you are available all day for all teams
If you have time or lift constraints, please put MAYBE and put a note saying the time constraint that your son CANNOT play eg: Available from 1pm onwards, Need to leave by 2pm, etc. It also helps if I know why you are constrained eg piano lesson! Or if you son needs a lift add note saying need lift from the club.
You need to be available from the meet time, not just the game time.