"Volunteer requirement once per family per season?"
There are some important caveats to this setting:
Families are complicated. You may have two kids in the club that share a mom but have different fathers. Because of this, this setting is technically 'once per user'. As long as the same parent registers their children, everything will work as expected. If two separate parents register two of their children, then it will attempt to 'charge' the volunteer hours to both. This should be an unusual circumstance as in most traditional families, one parent handles the registration.
One per season means once per Program Season in your Crossbar Dashboard. If you have a Travel Program and an 8U program and both have volunteer requirements, this setting will not prevent the second registration from getting charged. When you need to handle this, you have two options:
Modify the volunteer hours for those players after registration is completed.
Provide the parents with a custom registration that does not have the volunteer requirement.