Assuming that the overdrafts are "incidental;" i.e. not for large amounts, did not happen often, and they have been satisfied promptly in the past, I do not think you have a problem in changing your philosophy.
Several years ago there was a spate of lender liability lawsuits against banks that had routinely and systematically paid NSF items for their business customers. The amounts were large and the overdraft conditions were prolonged, in some cases, almost an "evergreen" loan. When the banks got nervous, the banks simply shut them off with no notice.
The "borrowers" argued that the overdrafts constituted a course of dealing on which they had relied and, when the banks shut them off, some actually went out of business. As foreign as it sounded to me at the time, some of the customers actually won. It was particularly helpful to their cause when they could quote bank employees as having said they would continue to honor the NSF items.
Note that I offered my opinion on the question before I offered the history lesson. The latter may be of no relevance to you at all. However, it's good to remember that extreme fact situations yield extreme results. If you have specific customers in mind I do suggest that you offer them the courtesy of telling them in advance about your change of philosphy, perhaps when you tell them about the availability of a line of credit.
Communicate with your customers whether it is required or not.
In this world you must be oh so smart or oh so pleasant. Well, for years I was smart. I recommend pleasant.