You will have a good time on any ship you go on. You like simple food so the quality of the food is not a major issue. You live in a dorm or campus apartment that needs to be fumigated at the very least of once a month. College students who live at home are only slightly better, that is, their room is off limits to the home's management. And this means that the room is a college room even if it is within the confines of a private home.
And what does this old guy know... my 21 year old son's university tuition for the winter quarter is within arm's reach of the person who is writing this.
RCCL and Carnival both have 3 and 4 day cruises that are reasonable but you should check other cruise lines as well. And while this is a long shot, you might find a 7 day cruise after January 1 that might be reasonably priced.
If I could, I would go with you.