Yes, weightgainers are classified as having at least 50 grams of carbs and a acceptable amount of fat.
http://www.bulknutrition.com/?cPath=34 See for yourself...
That being said, you have to structure your diet around weightgainer shakes. Of course too much carbs are counterproductive, and 30% of one's diet should come from fat. People, like myself, opt for weightgainer shakes for the carbs. I also don't see why you'd drink the 18 grams of fat right before bed. I understand your explanation, but I'll try and find some references on the web whether that's a bad idea or not. ;)