I do not understand your question. Who would you send a "change in terms" notice to as traveler's checks are purchased on an as needed basis. All you would need to do is modify you applicable product offering documentation as the travel card serves the same purpose as the travelers checks except I believe the card is more convenient and as such, this is not adverse to the customer. So, no you probably do not need to send a change in terms notice. Now you might was to send a statement stuffer or something so your customer are aware of the product change. This makes good marketing sense.
The opinion stated here is what it is, My Opinion.