OP, vet here. Please do not opt for any cleaning procedures without anaesthetic. No vet would ever advocate this, this is something some non-vets offer but isn't the equivalent of a vet dental cleaning.
This is just a descaling (there isn't the option to remove teeth which is almost guaranteed to be required in a CKCS this age) and even in the best behaved dog, the efficacy would be questionable.
It's more for healthy , young dogs with mild plaque build up and no actual dental disease. Even then, it's not something I'd suggest a client avails of.
Also, as there isn't anything protecting the airway, the bacterial films can go into the lungs.
If your vet feels the benefit of the dental outweighs the risk, go for it.
It's unusual for a Cavvie to not have heart disease at this age and the fact things are well controlled means the anaesthetic risk is low.
She'll be much happier with a healthy, pain free mouth.