Well, it obviously substitutes for something else, and I think kids pick up what they hear. So while it's certainly not a swear, it's kind of on the unprofessional side. I wouldn't be offended personally, but if the whole context were unprofessional, I'd consider saying something to the manager about the kinds of things staff say in front of customers.
By way of comparison, I was in a store standing behind a woman with 2 kids. It was right after that dramatic kidnapping of a toddler right out of the shopping cart in a WalMart. The mother and I were speaking very generally, sort of in "code" so the kids didn't know what we were discussing. The cashier jumped into the conversation but was way too graphic. I signaled to the cashier that one of the kids was right in front of the counter, and said "You know, we're trying to keep our conversation vague, for a reason...." She looked right at me, and started in again about the guy holding the child hostage and the police coming in to shoot the perpetrator! The mom hustled her kids right out of there and I reiterated that the children didn't need to hear that. She looked clueless. In retrospect, I wish I'd talked to the manager about professionalism in his staff and sensitivity around children.