If you're travelling as a group, renting an apartment for the week of the conference might be a good idea.
HAY4YOU offers short term rentals in the center of Copenhagen. Minimum stay is 7 days and you can't book earlier than 8 weeks before arrival. Rates for 3 bedroom apartments start at DKK 6.000 per week.
Airbnb has a list of private apartments available for short term rental.
The Adina Apartment Hotel Copenhagen offers 2 bedroom apartments. It is located north of downtown Copenhagen, further from the venue than the other hotels and hostels.