I knew there'd be more.
Puppies are adorable but are a LOT of work and training is a full time job for about a good year. BUT, your cats will do their part to train the dog. With an older dog, you probably still need to train but their personality will be further developed so you know what you're getting into.
But, ANY dog can be trained. Some are more difficult than others. Remember, dogs are pack animals. YOU need to be the Alpha dog in the pack for the dog to listen to you.
My boss always says "There are no bad dogs, only bad owners". I believe him.