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Your cats will accept a dog with time and some patience and good training from you.
They will be more likely to accept a small dog and it sounds like that is the breed that you have chosen.
Be sure that you socialize them well together when you bring the new dog home and don't allow the dog to chase/scare/hurt them. When you are not home, keep the dog in a crate because you can't monitor his behavior.
I think that, with time and patience, your cats will learn to love your new family member.
Let me know if you still have questions.