We have had Blake (Golden Doodle) at home for 2.5 weeks. He is 11 weeks old and are two cats have been with us for a couple of years. One cat has already put him in his place and generally ignores Blake and stays high, whilst the other cat still hisses continuously and this causes Blake to bark continuously. Two problems here really - the relationship with the cats and the barking.
Does your cat have a cat tree? If not, it is recommended that you buy a tall cat tree as a refuge area for cats. After all, dogs have more energy than cats.
Your dog should be trained to help him integrate into your home more quickly.