Hi Dana, I assume you are taking the 3-nighter that leaves Friday. I'm in San Diego and the rain has been rather sporadic ... most seems to be coming down at nighttime.
The Paradise has so much to do indoors, so I don't think it will be a problem. Although the kids may need to forego the pool due to the cool weather, but Camp Carnival has plenty to keep them entertained ... you should sign them up for that.
In port, in Ensenada there is a large terminal building with shops inside in which you can do some shopping without venturing into the rain too much (other than walking off the ship for 50 feet or so).
Here is a link to an article tat I wrote about what to do in Ensenada: