I was just on the Magic Christmas cruise last month.
One afternoon they had a "Chinese buffet" and there was a very nice sushi bar and they also had miso soup.
Regarding milkshakes, we brought our own waterbottles with large openings.
We put ice cream in the provided cups and then put it in our bottles, added some chocolate syrup, and then walked over to the milk machine and added milk (again from their cup). Shake and there you go, milkshake.
Make different flavors using whatever flavors are offered. We also had a strawberry shake.