I reckon you can do it...an extra week would allow you to get another long run in but as you dont have that time you cant....two week taper might not be enough.
I never covered more than about 25 miles for my 1st ultra (50 miles).
Given that next w/e is a BH I would recommend that if at all possible you go out and do a 30 miler (SLOWLY)......put some wlaking breaks in, then the next day, or perhaps on the monday, go out and do about 15-20 miles......but listen to how you are feeling.
Back to back runs are good training.
Pace will be critical in both your training, and also the event itself.