We didnt have 'designer breeds' in our system so yes, would put them in as mixes. I coached the staff to ask "Is their coat/size/etc more like a breed a or more like breed b" and then explained we priced grooming by breed so needed to best resemblance to make an accurate estimate.
This.
If you're calling me and telling me you want to bring in your cavalier, or golden retriever, I have a pretty good idea of the dog's size, coat condition, etc.
If you call and tell me you've got a Cavapeekachon, I have no idea what that dog's coat is like, how big it is, what the heck I'm expected to do to it. A good portion of the time I really honestly have no idea what mix of breeds the people are even talking about, the names are so convoluted.
And considering just about every client I've ever said this to has returned every 6 weeks, often times they recommend us to friends, and send us quite lavish holiday gifts and tip very well, I really don't think they're very offended. People get more offended when you tell them their dog has an ear infection ("well he must have just caught it while he was there.") or that their dog needed to be muzzled ("he's SO well trained though, my husband watches the dog whisperer and just pins him down whenever he's bad") than they do when you tell them their dog is a mixed breed.