Like PatP, I would have done it differently if I'd known.
My last dog (a border terrier) came as a puppy and always treated the resident cats with respect. So, when we got Bonnie, I thought it would be the same- let them get on with it. For our youngest cat, that's fine, she's happy to bop Bonnie on the nose, suffers a wash every now and again, but there's no sleeping together whatsoever. The older cat moved into the front garden when Bonnie arrived. She now has a bed in the porch and won't come into the main house unless she knows that Bonnie is out. Two years later.
Guess it depends on the cat, but I wouldn't leave it to them next time.