If you don;t mind sharing a room with others. I recommend this hostel at Soda Spring.
The photos on the photo page are accurate. It is clean and comfortable. The owners are super nice. It within 30 minutes to most N. Tahoe resorts. There is a small bar and cafe downstairs. I think you can easily rent the whole place for the gathering. The owner tells me there are 20 beds, including 2 queues available. It only costs a little over $500 (please double check this number) to rent the whole place. They also have extra cots available if you need them. If there is some interest, someone probably could ask the owner to see if they can act as organizer.
I have just a happy customer, like the owner's family very much. I do not have any relationship with this them.