The best way we find doing exactly what you describe, is by adding all these charges in auto contract,
So like this you never forget to bill it.
You can always delete the charge in contract, if he isn’t using that service you are charging for.
And you can always edit the charge, if at some point they decide they do want the service and it won’t affect the existing children receiving the service charge.
It also has a pop up warning so if you edit a contract item and it has multiple children on it how you want to split the charge.
As a JL user I think this way will address all your concerns.