I might as well answer too. Sure, you can change your idea technically. For nanowrimo you can change to a different book on day 1. You don't necessarily have to write the one you are prepping per say. Last year, I prepped three novels. 1 young adult, 1 adult urban fantasy and 1 adult fantasy. I wrote an unprepared romance/erotica (got almost 100k on it) and worked on the young adult novel (just over 25k done) in November.

Even if you don't use the prep you did on your novel right now, you can always use it later in the future. Thus why I prepare more than one novel now even though I'm not writing them all.

I would imagine, considering the fact that you not only enter weekly quickie almost every week (when you're not the judge) and you enter other contests consistently (like paradise cove, sensual moments and such) that going for a collection of erotic short stories would work out for you. You could get 50,000 words worth of them in a month, I am certain. And you have this week off from quickie, so you probably could get some outlines and such done this week. I know you can do it if you want. So, if that's what you really want to do for nanowrimo, I say go ahead.