If you do a Google search on "debit card fraud" you will get plenty of materials which you can use to build your customer communications. FTC
I'm not overly impressed with the presentation in this one,
but note that it mentions not using your card in situations where it will be out of your sight; e.g. when the server leaves the table process the charge.
I'm curious about the prohibitions against disclosing problems to customers that BetsyS referred to, but it's outside my experience. I will note that a friend who is a trust officer routinely used a debit card for entertaining at a local restaurant and his bank (not a small one) called and told him to please use his credit card there from now on.