Hello--
I would make sure that your dog is tolerant of a cat before introducing a new one into the home. Since your puppy was raised with the other feline, he may be more tolerant of that cat specifically, rather than cats in general, but many dogs do do well with felines.
I would suggest a more laid back breed of cat, such as a ragdoll, ragamuffin, persian, himalayan, American Shorthair, selkirk rex, siberian, or other less active breed. High strung cats, such as some of the oriental breeds may not be a good choice to have with a dog. A LOT depends on the way the kittens are raised by the breeder. Any breeder that also has dogs and allows interaction between the species would be worth talking to. Also, make sure you have the ability and perserverance to supervise your two pets constantly until there is absolutely no doubt that there will be no injury to the new kitten, whether accidental or intentional on the part of your Cavalier. Eventually, the cat will learn to stay out of the way of the dog, if it is too rough for him/her.
Please let me know if I can help further in any way!
Feline Healthcare
16 yrs health care mgmt & issues relating to cats, reproductive issues and multicat environments