NYC hotels are notoriously small and, to be honest, most won't have the floor space for nine people. You'll probably have better luck with space - and with avoiding hotel staff - at one of the chains (but avoid the Grand Central Hyatt as their room sizes are a crap shoot).

Which hotels are you looking at? Any chance you guys can afford a suite somewhere? Or a normal room at the Doubletree Suites or Embassy Suites?

You might also want to head over to the Travel Bidding forum for advice on whether Priceline for two rooms would actually be better for you.

About 7 years ago, my friends and I used priceline for a room at the Renaissance in Times Square over St. Patrick's Day. Fairly large by NYC standards. Plenty of room for four, you'd literally be tripping over people if you squeezed seven, but I don't think nine would fit.