As the supplier you should back yourself as to whether its likely that your changes will cause an issue or not. If so, issue a warning, otherwise don't.

The reason I say this is not for your customer's benefit but for yours. I've seen people get all knotted up with process because someone had the bright idea that the customer should be notified when absolutely anything changes behind the scenes - just in case. This abundance of caution will make your life a misery, and stops any rapid movement. It also desensitizes the customer, who gets used to your notifications and eventually decides they can ignore them.