Rehoming my best friends

Me (34F) and my partner (37M) are 8 months pregnant, I have two cats (3 and 2 years old) and a puppy (7 months old). My partner has a 6 year old daughter.

These cats are my world. I love them to pieces. I'm tearing up even as I write this.

The cats and dog do not get along, to the point where the cats will constantly hit the dog for amusement. I tried to slowly introduce them but the book not 6 months in, there's still hissing and slapping. Especially from my one cat that was born sick and anxious. The dog is so sweet and doesn't react. He keeps to himself and is generally very quiet.

Keeping them separated and watching them all the time is so time consuming. Making sure they all get enough attention and play time then cleaning up after them is already exhausting.

I have a friend who the cats adore that may be willing to keep them. They spend a lot of time with that friend already. The thought of doing this kills me inside. Those cats were my everything. But I can't imagine things will get much easier.

Would I be doing the wrong thing here?