Ummm - ya I would not apply any holding fee to their CARE when they start... it is a holding fee it covers your 'lost income' for keeping that space open for them and it is non refundable should they change their mind and not start.
Same with the security deposit which I would also charge which is equal to two weeks fees and ensures that you are given proper notice to terminate the contract and find a replace that is only applicable to the last two weeks of CARE and with proper written notice before hand ... should they change their mind and not enroll after having signed a contract they LOOSE the deposit!
It is like when you put in an offer on a new house you have to pay $1000 or something like that and if the other person accepts that offer and than later YOU change your mind you do not get that $1000 back ... it is absorbed by the realtor for their work in putting in the offer and accepting the offer and so forth!