Prep's dragging along for me, too, at the moment, and I'm not sure I'll make it to the end in time.

However, like in your case, it's now more the story building and evolving before my mind's eye now that has me going, instead of really "winning" Prep.

Of course, that doesn't keep me from trying.

Oh, and of course you can do NaNo! If it stays like this, your story will kinda write itself, always following the MC(s) on the heel, them taking the lead.

Let them!