Use the “wet flannel” trick - before introducing your pup, dampen a flannel with warm water and rub over the pup, then rub over the cats, back to the pup and so on a few times each. That way you are cross scenting.
Give the cats space and a safe place to get to that your pup cannot, perhaps behind a stair gate.
Don’t allow your pup to chase the cats, not even in play and however funny (and it will be) as you are teaching your dog it’s ok to chase other animals, you will thank me for this when your pup hits the teenage phase!
Otherwise, supervise the meeting, monitor play and when your pup gets to around 7Kg make sure your cats are safe…..my first cocker put the cats back out through playing!
Some cats will never warm to a dog but if yours are used to dogs being around them, even at a distance, it shouldn’t be such a shock!
Good luck, Jayne