There two different aspect to this question.

One is what YOU declare as your income and the answer to that is ALL fees. Late payment fee, late collection fee, all money paid to you as result of your business and so must all be declared as your income to CRA.

Second part is what is write on THEIR tax receipt. My accountant clear that tax receipt for client is so they can claim their child care fees. They do not get to claim extra fees they had to pay because they not arrive on time or pay promptly. Those are not costs of care but costs of them fail to meet contracted terms, penalties not fees for service. Their receipt should only detail the actual fees.