the most important thing in the cats minds, is that they need to be 110% sure that the dog absolutely won't chase them, and won't do anything silly- they're not going to trust him at ALL, if he's unpredictable, and can't mind his business and stay out of theirs.this is exactly why you do not want to introduce a puppy.
puppies aint smart or predictable, and they don't know their strength. also avoid breeds like greyhounds, lurchers, jack russells, terriers, etc, unless you know that the individual dog is very lazy and laid back and doesn't chase or grab- and he's proven this to be true in your experience.
for your sanity, you need to be 110% sure that the dog knows his place in the pack order (which is way down below even the smallest cats) and you need to be sure that he will do exactly what you tell him to do, every time you tell him, before you even dream of leaving the two groups together under minimal supervision (if he won't listen to you, he aint gonna respect the cats authority, and as he's more likely to kill them accidently than the other way round, he needs to respect them when they say 'no').
the best way of introducing cats to dogs in my experience, has been to start by getting them used to the dog smell -and vice versa, before they meet face to face. swap out blankets, let people sniff around each others rooms while the other parties are elsewhere (don't carry them across hallways out of arms reach of each other, or anything, use a third room to rotate them around out of sight).
when the dog is out in a communal area and about to be introduced to the cats initially, let him get his bearings, make sure he's chilled out (maybe that he's been on a good long hike and had a big dinner and fancies a nap pretty soon) and get him relaxed and settled (no playing games for a while), and then when you think he's calm enough to be there with cats around, get somebody else whom the cats know, to let them out into the space. initially that dog needs to be on a leash, and to stay right at your side- clip him to your belt if you need to. you need to be able to get him to sit, and stay, confidently, at the speed of lightning.
you need to have positioned yourself with the dog, somewhere that the cats won't charge into you both by surprise (so you sat on a chair that they can see across the room before approaching is good, just around the corner of the hallway is bad!). it's important that cats have places that they can be which are up pretty high (they feel safer) and that they can get somewhere that he can't (leave a closet door wedged open just enough for them to sneak in, or use a babygate to block off a room, or something.
the dog needs to be doing his sitting and staying when the cats first see him (which they should instigate at their own pace) and he needs to sit and stay while they approach, walk by, give him a suspicious look- even if they come right up to him (only if they want to) and sniff him, and even if they hiss- and then they'll likely leave in a small flounce if he doesn't do anything (they're just telling him not to mess with them). if they actively approach and then go as far as to stalk, verbalise threats, pounce, and strike him, then honestly, they're probably not gonna come around long term. that's relatively unlikely to happen unless they've been rescued from outside or had very negative dog experiences in their pasts, but if it does, don't grab at the cat to get them off the dog unless it's totally necessary- it's always better to startle them with a loud noise or surprise (throw a saucepan across the room, get your friend to yell and clap their hands or drop a jar of pennies- give them a reason to snap out of attack mode and bolt for cover, that isn't you picking the dogs side in a fight, in their mind. otherwise they can start to redirect aggression at you, and/or pick on the dog when you're not looking.
when the two parties meet, keep talking to the dog, keep him focussed on a treat, keep him still and dog and calm, get a friend to distract the cats a little with toys, treats, dinner, etc... but
that dog needs to be still, and stay put.... if he can't, don't let them share a space until he can. once they've got used to his presence, you can give him more line, let him walk about, etc, watching him to see how he interacts with them. but take your time. if the cats get stressed, don't push them.. wait a bit before reintroducing them. consistency is really key.