What kind of bikes have you had before? What kind of terrain will you be riding on? I find it a little strange that you said you were experienced with carrying passengers on a bike, yet not know if a 250cc would have enough power.
For an experienced rider wanting a cruiser, I’d say go with a 650, at least, even without a passenger. There are a lot of people who think a 650 cruiser is too small to carry a passenger comfortably over long distance.